الجزء السادس من معجم الاجهزة F

fabrication 1. A general term for parts manufacture, especially structural or mechanical parts. 2. The assembly of components into a completed structure.

Fabry-Perot A pair of highly reflective mirrors, whose separation can be adjusted to select light of particular wavelengths. When used as a laser resonator, this type of cavity can narrow the range of wavelengths emitted by the laser. face 1. An exposed structural surface. 2. In a weldment, the exposed surface of the fusion zone. faceplate 1. A circular plate that is attached to the spindle of a lathe. The plane of the plate is perpendicular to the spindle axis. Faceplates are used to attach and align certain types of workpieces. 2. A protective cover for holes in an equipment enclosure. 3. A glass or plastic window in personal protective gear such as welding helmets, respirator masks, or diving masks. 4. A two-dimensional array of separate optical fibers that are fused together on order to strongly direct light forward. facet The plane surface of a crystal or fracture surface. face-to-face dimension The dimension from the face of the inlet opening to the face of the outlet opening of a valve. [ANSI/ISA75.05.01-2000] facing 1. The act of machining a flat, planar surface in a lathe turning by positioning a single-point tool against the workpiece at the axis of rotation. The tool is then moved radially outward so that it cuts a spiral path in a plane that is perpendicular to the axis of rotation. 2. Fine molding sand that is applied to the surface of the mold cavity. facing, flange The finish on the end-connection gasket surfaces of flanged or flangeless valves. [ANSI/ISA-75.05.01-2000] facsimile 1. A machine for sending digitized copies of documents by telephone. 2. A system for utilizing telephone transmission apparatuses to send written or graphical information to a remote location. A facsimile or "fax" consists of a transmitter, which scans the hard copy record and converts its image into an electrical signal wave, and a receiver, which converts the electrical wave into its final pictorial form and registers it on a record sheet. factorial designs Designs of experiments in which multiple input variables are varied

simultaneously at two or more discrete levels in every possible combination. factory calibration The tuning or altering of a control circuit or device by a manufacturer to bring it into specification. factory sealed A construction in which components that are capable of initiating an internal explosion as a result of arcing, spark_ing, or thermal effects under normal conditions are isolated from ttte wiring system by means of a factbry;-instifUed flameproof seal or joint. [ANSI/I~A712.22.01-1998 (lEe 60079-1 Mod)] fading A drop or a slow undulation in signal intensity that is caused by changes in the properties of the transmission medium.

Fahrenheit A temperature scale in which the freezing point of pure water occurs at 32째F and the span between the freezing point and boiling point of pure water at standard pressure is defined tb be 180 scale divisions (180 degrees). fail-closed A condition in which the valve closure member moves to a closed position when the source of actuating energy fails.

[ANSI/ISA-75.05.01-2000] fail-in-place A condition in which the valve closure member stays in its last position when the actuating energy source fails.

[ANSI/ISA-75.05.01-2000] fail-open A condition in which the valve closure member moves into an open position when the actuating energy source fails.

[ANSI/ISA-75.05.01-2000] fail-safe 1. A characteristic of a particular valve and its actuator such that the loss of actuating energy supply will cause a valve closure member to be fully closed, fully open, or remain in the last position. [ANSI/ ISA-75.05.01-2000] 2. Any protection against the effects of failure of equipment, such as a fuel shut-off when flame in a furnace is lost. 3.

Referring to the capacity to go into a predetermined safe state when a specific malfunction occurs. [A SI/ISA-84.01-1996; ANSI/ISA77.13.01-1999]

F

I A

HOT FAIL SAFE: TO CLOSED POSITION

FAIL SAFE: TO OPEN POSITION

Fail-safe Conditions that Remove Energy fail-safe device A component, system, or control device that is designed so that it

193

II

failure mode / fastener

II

places the controlled parameter in a safe condition when there is a power interruption, controller malfunction, or the failure of a load-carrying member. failure mode The position to which the valve closure member moves when the actuating energy source fails. [ANSI/ISA-75.05.012000] failure rate A measure of component reliability that is usually expressed as the probability of failure after a specified length of time in service.

FAILURE RATE

+

NUMBER OF FAILURE UNITS TIME

a

+

"Bathtub Curve" of Unit Failures FAIS Factory Automation Interconnection System [pronounced fice]. Initially a Japanese effort to commercialize a Mini-MAP subsystem optimized for manufacturing cell network applications. See Mini- MAP. fall The chain, rope, or wire rope that is used to lift tackle. fall block In lifting tackle, a pulley block that is attached to the load and rises or descends with it. fall time The time that is required for the trailing edge of a pulse to fall from 90 to 10 percent of its amplitude. The time required for a component to produce such a re5ult. false add To form a partial sum, that is, to add without carries. false Brinelling The fretting between the rolling elements and the races of ball or roller bearings. false set The rapid hardening of freshly mixed cement, mortar, or concrete with a minimum evolution of heat. Plasticity can be restored through mixing, without adding more water. fan A rotating mechanism that is used to induce movement (currents) in air or other gas, such as in a circulation, ventilation, or exhaust system where large volumes must be delivered. It usually consists of a paddle wheel or screw, with or without a casing, fan-inlet area The inside area of the fan outlet.

fan performance A measure of a fan's operation in terms of volume, total pressures, static pressures, speed, power input, and mechanical and static efficiency, at a stated air density. fan-performance curves The graphical presentation of total pressure, static pressure, power input, and mechanical and static efficiency as ordinates as well as graphical presentation of the range of volumes as abscissa, . all at conslant speed and air density. fangbolt A bolt thqt has a triangular head with sharp projections at the corners and is used primarily to attach metal parts to wood. fan-in The maximum number of electrical inputs acceptable by a logic circuit. fan-out Within a family of logic circuits, the maximum number of electrical inputs to other circuits that an output or given circuit can drive. farad The metric unit of electrical capacitance.

Faraday rotation'路 A rotation of the plane of polarization of light that is caused by the application of a magnetic field to the material transmitting the light.

Faraday rotator A device that relies on Faraday rotation to rotate the plane of polarization of a beam of light passing through it.

Faraday rotator glass is a type of glass whose composition is designed to display Faraday rotation. far field Distant from the source of light. This qualification is often used in measuring beam quality, to indicate that the measurement is made far enough away from the laser such that local aberrations in the vicinity of the laser have been averaged out. far-infrared laser Generically, this term could be taken to mean any laser that emits in the far infrared, a vaguely defined region of wavelengths from around 10 micrometers to 1 millimeter. This family of lasers depends on optical pumping by an external laserusually a carbon dioxide laser. fast break In the magnetic particle testing of ferromagnetic materials, a fast break means interrupting the current in the magnetizing coil so as to induce eddy currents and strong magnetization as the magnetizing field collapses. fastener 1. Any of several types of devices that are used to hold parts firmly together in an assembly. Some fasteners hold parts firmly in position but allow free or limited relative rotation. 2. A device for holding a door, gate, or similar structural member closed.

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fast-Fourier transform (FFT) / FCS fast-Fourier transform (FFT) A Fourier transform that employs the Cooley-Tukey algorithm to reduce the number of operations. fast-Fourier transform (FFT) analyzer An instrument that converts frequency-domain information into time-domain information (or vice versa) by way of a fast Fourier transform algorithm. fat client In client/server architecture, a client that performs the bulk of the data processing operations. The data are stored on the server, however. The term usually refers to software, but it can also apply to a network computer that has relatively strong processing abilities. See thin client. fatigue The progressive fracture of a material by the formation and growth of minute cracks under repeated or fluctuating stresses.

The maximum value of such fatigue is less than the material's tensile strength and is often wholly within the elastic-stress range. fatigue life The number of stress cycles that a material can sustain before fracturing, for a given set of fatigue conditions. fatigue notch factor The ratio of the fatigue strength of an unnotched specimen to the fatigue strength of a notched specimen of the same material and condition. The notch that is used has a specified size and contour, and the strengths are compared at the same number of stress cycles. fatigue notch sensitivity An estimate of the effect of a notch or hole on the fatigue properties of a material. It is expressed as q = (K 1)/K t - 1), where q is the fatigue notch senSItivity, Kf is the fatigue notch factor, and K t is the stress concentration factor for a specimen of the material that contains a notch of a specific size and shape. fatigue strength The maximum stress that ordinarily leads to fatigue fracture in a specified number of stress cycles. If the stress is not completely reversed during each stress cycle, the minimum stress also should be given. See also endurance limit. fault 1. A physical condition that causes a device, a component, or an element to fail to perform in a required way. Examples include a short circuit, a broken wire, or an intermittent connection. 2. A defect of any component upon which the intrinsic safety of a circuit depends. 3. The failure of any part of a computer system. 4. A short- or open-circuit defect in any part (i.e., a component, connection, separation, or insulation). Note: If a fault leads to faults in other parts that impact the type of protection that the circuit provides, then the primary and subsequent fail-

r

ures are considered to be a single fault. [ISA12.02.01-1999 (IEC 60079-11 Mod)] 5. An abnormal condition that may cause a reduction in, or loss of, the capability of a functional unit to perform a required function.

[IEC 1508, Part 4] fault, intrinsically safe system A defect or the electrical breakdown of any component, spacing, or insulation that alone or in combination with other defects or breakdowns may adversely affect the electriCal or thermal .. characteristics ofthe intfinsically safe sys- . tem. If a defect or breakdown leads to defects or breakdowns in other components, then the primary and subsequent defects and breakdowns are considered to be a single ;,. J~ult. When analyses or tests for intrinsic safety am mad~~'certi1in components may be considered to be exempt from fault. See also protective component. [ANSI /ISA-12.01.011999] fault isolation test (FIT) A unit of measurement for product reliability that is equal to 10-9 failures per hour. fault tolerance The built-in capability of a system to provide the continued, correct execution of its assigned function in the presence of a limited number of hardware and software faults. [ANSI/ISA-84.01-1996] fault-tolerant Of a system, haVing the builtin capability to provide continued, correct execution of its assigned function in the presence of a hardware and/or software fault.

[ANSI/ISA-77.13.01-1999) fax See facsimile. faying surface Either of two surfaces that are in contact with each other in a welded, fastened, or bonded joint or in one that is about to be welded, fastened, or bonded.

FC Fail closed; default mode of the final element in a process, typically a valve.

FCC Federal Communications Commission; U.s. agency involved with any radio-transmitted communications. 2. See "frame code complement."

F-center laser A solid-state laser in which optical pumping by light from a visible-wavelength laser produces tunable, near-infrared emission from defects-ealled "color centers" or "F centers"-in certain crystals.

FCFS First come, first served; the order of packet transmissions in multiple access to linear bus LANs, where stations may place reservations in a separate logical channel (as compared with round robin method).

FCS Frame Check Sequence method of transmission error detection.

195

I

l'UA I feedforward control

II

FDA Food and Drug Administration (United States); U.s. agency involved with the validation of all systems and facilities manufacturing food, pharmaceutical, and medicalrelated products for human or animal use.

FOC Final control device, such as valve, motor drive unit, SCR, etc.; see final element.

FOOl Fiber distributed data interface; ANSI standard for fiber-optic links with data rates to 100 Mbps; two 50 Mbs counter-rotational token rings, synchronous, prioritized; see路 COOl. \ FOM Frequency division multiplexer (or multiplexing); device that divides available transmission frequency range into narrower banks, each of which is used for a separate channel.

FDX Full duplex; mode of communication in which data may simultaneously flow in both directions (4-wire).

FEA Finite element analysis software for design. feasibility study Any evaluation of the worth of a proposed project based on specific criteria.

Fed. Reg. Federal Register. A daily publication of the U.s. government that details proposed and final rules as well as other federal business. feed 1. The act of supplying material to a process or to a specific processing unit. 2. The material supplied. Also known as feedstock. 3.

A forward motion that tends to advance a tool or cutter into the stock in a machining operation. feedback 1. A process signal that is used in control as a measure of the response to control action. 2. The part of a closed-loop system that automatically brings back information about the condition under control, for the sake of comparing that information with the desired condition. 3. A signal produced by a measuring device that is proportional to the magnitude of a controlled variable or the position of a control element.

[ANSI/ISA-77.44.01-2000j feedback control An error-driven control system in which the control signal to the actuators is proportional to the difference between a command signal and a feedback signal from the process variable being controlled. See control,jeedback. feedback control signal The output signal that is returned to the input in order to achieve a desired effect, such as fast response. feedback elements See elements, feedback.

feedback loop The components and processes that are involved in correcting or controlling a system by using part of the output as input. See loop, closed (feedback loop). feedback oscillator An amplifier circuit in which an oscillating output signal is coupled in phase with the input signal. The oscillation is maintained at a frequency that is determined by frequency-selective parameters of the amplifier and its feedback circuits. feedbacl< ratil:? .1A a control system, the ratio of the feedback signal to a corresponding reference input. feedback signal A signal that is derived from some attribute of the controlled variable, or from it control system output, It is combined with one or more input or refer"ence sighiffs' to produce a composite actuating signal. See

signal, feedback. feeder 1. A conveyor that is adapted to control the rate of delivery of bulk materials, packages, or objects to a specific point or operation. 2. A device for the controlled delivery of materials to a processing unit. 3.

In metal casting, a runner or riser so placed that it can deliver molten metal to the contracting mass of metal as it cools and solidifies, thus preventing voids, porosity, or shrinkage cavities. feed forward A control action that is taken to compensate for the effect of a sensed input disturbance. Also called open-loop control or anticipatory control. See open-loop control. feed forward control A method of control that compensates for a disturbance before its effect is felt in the output. It is based on a model that relates the output to the input at the point where the disturbance occurs. In distillation, the disturbances are usually feed rate and feed compositions. Steady-state feed forward models are usually combined with dynamic compensation functions to set the manipulative variables. Such models are combined with feedback adjustment (trim) to correct for constraints on the accuracy of control models. See control,jeedforward.

SETPOINT

DISTURBANCE

FEEDFORWARD CONTROLLER

MANIPULATED VARIABLE

PROCESS

CONTROLLED VARIABLE

196 -- ._-----_..

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feedforward control action / ferrite feed forward control action Control action in which information concerning one or more external conditions that can disturb the controlled variable is converted into corrective action in order to minimize deviations of the controlled variable. Feedforward control is usually combined with other types of control to anticipate and minimize deviations of the controlled variable. feed pipe A pipe through which water is conducted into a boiler. feed rate The relative velocity between tool holder and workpiece along the main direction of cutting in a machining operation. feed screw An externally threaded rod that is used to control the advance of a tool or a tool slide on a lathe, a diamond-drilling rig, percussion drill, or other equipment. feedstock Mnterial that is delivered to a process or processing unit, especially raw material delivered to a chemical process or reaction vessel. feed through A contact on a printed circuit board that connects one physical layer of interconnections with the next, and in doing so passing through the insulating material that separates them. feed through error A signal that is caused by a coupling from reference input to output when the digital-to-analog converter logic inputs are all low. Expressed in mY or dB relative to VREF . feed trough A trough or pan from which feedwater overflows in the drum. feed water Process water that is supplied to a vessel such as a boiler or still, as opposed to circulating water or cooling water. feedwater flow-control system A control system that uses input signals derived from the process to regulate feed water flow to the boiler. This is done to maintain adequate drum level according to the manufacturer's recommendations. [ANSI/ISA-77.42.011999] }I

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STREAM FLOW

UPSETS

A Three-element Feedwater Regulator

197

feedwater treatment The treatment of boiler feed water by the addition of chemicals so as to prevent the formation of scale or to eliminate other objectionable characteristics. field-effect transistor (FET) A unipolar multielectrode semiconductor device in which current flows through a narrow conducting channel between two electrodes and is modulated by an electric field applied at the third electrode. femal~ brand). tee. (F~.p In tubing to a pipe connector, a tee that aliows two tubes to be joined to a pipe. The female pipe thread connection is perpendicular to the axis shared by the two tubing connections. female connettor (FC) In tubing to a pipe connector, a connector that has a female pipe thread connection on one end and a tubing connection on the other. female elbow (FE) In tubing to a pipe connector, a 90째 change in direction that has a female pipe thread connection on one end and a tubing connection on the other. female fitting An element of a connection in pipe, tubing, electrical conductors, or mechanical assemblies that surrounds or receives the mating (male) element. For example, the internally threaded end of a pipe fitting is termed "female." female run tee (FRT) In tubing to a pipe connector, a tee that allows two tubes to be joined to a pipe. The female pipe thread connection and one of the tubing connectors share a common axis.

FEP Front end processor; dedicated processor to perform communication functions to offload other processors within same device; it is that portion of the system that first receives process or plant data, usually for signal conditioning and/or multiplexing.

Fermat principle Also called "the principle of least time." According to it, a ray of light traveling from one point to another follows the path that takes the least amount of time (including any reflections and refractions that the ray may suffer). Stated another way, the optical path is an extreme path, in the terminology of the calculus of variations. ferric percentage Actual ferric iron in slag. It is expressed as a percentage of the total iron calculated as ferric iron. ferrite A low-density ceramic material whose composition includes divalent metal, such as cobalt, nickel, manganese, or zinc. Cores made from these metals have very low eddy current loss and are useful in some mechanical-to-current transducers as well as in high-

ferroalloy / fiber optics

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frequency circuits and as magnetic dust cores in computers. ferroalloy An alloy, usually a binary alloy, of iron and another chemical element that contains enough of the second element to be suitable for introduction into molten steel.

The result is alloy steel. In the case of ferrosilicon or ferroaluminum, the introduction of the second chemical element produces controlled deoxidation. ferrodynamic instrument An electrodynamic instrument in which the presence of ferromagnetic material (such as an iron core for an electromagnetic coil) enhances the forces that are ordinarily developed in the instrument. ferrography Wear analysis that is conducted by withdrawing lubricating oil from an oil reservoir and using a Jerrograph analyzer to determine the size distribution of the wear particles that are picked up as the oil circu- . lates between moving mechanical parts. The technique may also be used to assess the deterioration of human joints or jointreplacement prostheses by analyzing for the presence of bone, cartilage, and prosthetic-material fragments in human synovial fluid. ferromagnetic material Any material that exhibits the phenomena of magnetic hysteresis and saturation, and whose permeability depends on the magnetizing force. All of these characteristics are exhibited by the chemical element iron. ferrometer An instrument for measuring magnetic permeability and hysteresis in iron, steel, and other ferromagnetic materials. ferroresonant power supply A power supply that uses a ferroresonant regulator consisting of a ferroresonant transformer AC tuning capacitor, a rectifier, and a DC filter capacitor.

These make it possible for the power supply to provide reasonable regulation of line voltage. This is the least expensive yet most reliable power supply because of the simple circuit. ferrous alloy Any alloy that contains at least 50 percent of the element iron by weight. ferrule 1. A metal ring or cap that is fitted onto the end of a tool handle, post, or other similar member to strengthen and protect it.

2. A bushing that is inserted in the end of a boiler flue to spread and tighten it. 3. A tapered bushing that is used in compression-type tubing fittings to provide the wedging action that creates a mechanical seal. 4. An element of a fiber-optic connector that is typically used to house or align fibers.

FET Field-effect transistor; unipolar multielectrode semiconductor device in which current flows through a narrow conducting channel between two electrodes and is modulated by an electric field applied at the third electrode. fetch 1. To obtain the data from an address memory location. 2. The process of obtaining the data.

F format In FORTRAN, Fw.d indicates that w characrers.are}o be converted into a floatingpoint mixerl number, with d spaces reserved for digits to the right of the decimal point.

For example, F6.3 yields 24683 as input, 24.683 internally, and 24.683 as output.

FI Fail indeterminate; default mode of a final element in a process, typically a valve. fiber channel An emerging optical communications standard issued by an ANSI working group. It transmits 100 Megabytes/ second. fiber loss Attenuation (deterioration) of a light signal in optical fiber transmission.

Rellected light intenSity

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125

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f7S

200

Oistilnce 10.001 In) Output vs OiSlilnce

fiber metal A material that is composed of metal fibers that have been pressed or sintered together, and that may also have been impregnated with resin, molten metal, or other material, which later hardened.

Fiber-optic gyroscope A device in which rotation speed is measured studying changes in the wavelength of light going in different directions through a long length of optical fiber wound many times arolmd a ring. fiber optics 1. A medium that uses light conducted through glass or plastic fibers to transmit data and make optical measurements and observations. 2. Glass or other dielectric fibers whose refractive index decreases with the radial distance from the center of the fiber's cross section. Thus, a light beam that enters one end of the fiber is constrained to travel the length of the fiber and exit the other end with very little attem:ation. 3. A transmission technology in which modulated light-wave signals, generated by laser or LED, are propagated along a (typically) glass or plastic medium, then demodulated into electrical signals by a light-sensitive receiver.

198

fiber-optic system / fieldbus

I

fiber-optic system 1. A relatively new method of data transmission in which light­ transmitting fibers are used to connect sen­ sors to the computer. Fiber-optic systems have very good immunity from noise. 2. Any system that performs the analytical observa­ tion of measurements by employing the transmission properties of glass, plastic, polycrystalline, or crystals materials-fiber optics. fiber 1. Th~ characteristic of wrought metal that indicates directionality and can be revealed by etching or fractography. 2. The pattern of preferred orientation in a poly­ crystalline metal after directional plastic deforma tion ~u.ch as is caused by rolling or wiredrawing. 3. A filament or filamentary fragment of natural or synthetic materials that is used to make thread, rope, matting, or fabric. 4. In stress analysis, a theoretical ele­ ment that represents a filamentary section of solid material aligned with the direction of stress. Fiber is usually used to characterize nonuniform stress distributions, as in a beam that is subjected to a bending load. . Fiber-optic Inter Repeater Link An early implementation of a subset of the IEEE 802.3 lOBASEFL standard that was designed to con­ nect fiber-optic repeaters at 10 Mbps. Used by various Ethernet manufacturers to pro­ duce network and port interface cards as well as media attachment units (MAUs)/ transceivers. See media attachment units (MAW. fibers and flyings Materials that are not nor­ mally in suspension in air and are of larger particle size than dusts. Fibers and flyings include cotton linters, sawdust, textile fibers, and other large particles that are usually more a fire than an explosion hazard. [ISA­ 12.01.01-1999] fibers and flyings, easily it;nitable Fibers and flyings that can easily be set aflame, including rayon, cotton (including cotton linters and cotton waste), sisal or henequen, istle, jute, hemp, tow, cocoa fiber, oakum, baled waste kapok, Spanish moss, excelsior, and other similar materials. [ANSI/ISA­ 12.01.01-1999] fiber sensor A sensing device in which the active element is an optical fiber or an ele­ ment that is attached directly to an optical fiber. The quantity being measured changes the optical properties of the fiber in a way that can be detected and measured. fibrous composite A material that consists of natural, synthetic, or metallic fibers embed-

I

ded in a matrix, usually a matrix of molded plastics material or hardenable resin. fibrous fracture A type of fracture surface whose appearance is characterized by a smooth, dull gray surface. fibrous structure 1. In fractography, a frac­ ture with a ropy surface appearance, and is generally synonymous with "silky facture" or "ductile fracture." 2. In forgings, a charac­ teristic macrostructure that is indicative of metal flow Qurihg·tha (6iging process. It is manif~sted as a ropy appearance on a frac­ ture surface or as a laminar appearance on a macroetched section. A ropy appearance on

the fracture surface of a forging does not

carry the same implication as a ropy fracture

in other wrought metals and should not be

considered the same as a silky or ductile frac­

ture. 3. In wrought iron, a microscopic struc­

ture that consists of elongated slag fibers

embedded in a matrix of ferrite.

FIC Fieldbus Implementation Consortium; to implement SP50 as it evolves.

FICIM Fieldbus Integration into computer integrated manufacturing CIM; ESPRIT . project group 5206. fidelity 1. The degree of both physical and functional realism. 2. The degree to which a system, subsystem, or component accurately reproduces the essential characteristics of an input signal in its output signal. field The part of a computer record that con­ tains a specific portion of information. fieldbus A digital, serial, multidrop, two­ way data bus or communication path or link between low-level industrial field equipment such as sensors, transducers, actuators, local controllers, and even control room devices. A specific ISA SP50 (Fieldbus Foundation) standard for digital communications that operates at the lowest level of data commu­ nications (l/Os) in automation systems. It allows communication and interoperability among "smart" field devices and measure­ ment/ control system devices from multiple vendors. It also supports information access for the purpose of monitoring, control, and alarm tasks during plant start-up, operation, and maintenance. As this standard is devel­ oping and attracting interest, two versions are emerging: HI, for linking sensors and actuators to control devices, and H2, for functioning more as a full-blown data high­ way on a more sophisticated scale. Fieldbus serves as a local area network (LAN) for advanced process control, remote input/ out­ put, and high-speed factory automation

199

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Fieldbus Access Sublayer (FAS) / field weld

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applications. An eight-part fieldbus standard is under development by ISA and IEC. Fieldbus Access Sublayer (FAS) A messag­ ing sublayer that maps the Fieldbus Message Specification (FMS) onto the data link layer (DLL).

Fieldbus Messaging Specification (FMS) A specification that contains definitions of application layer services in Foundation Fieldbus. The FMS specifies services and message formats for accessing function block (FB) parameters, as well as object dictionary (00) descriptions for those parameters that are defined in the virtual field device (VFD). field coil A stationary or rotating electromag­ netic coil. field contact Also known as a trouble or sig­ nal contact, a field contact is the electrical contact of the device that senses the process condition. The contact is either open or closed. Annunciator field contacts are identi­ fied in relation to process conditions and the annunciator operation, not in relation to the disconnected position of the devices. [ANSI/ ISA-18.1-1979 (R1992)] field contact, normally closed (NC) A field contact that is closed for a normal process condition and open when the process condi­ tion is abnormal. [ANSI/ISA-18.1-1979 (R1992)] field contact, normally open (NO) ·A field contact that is open for a normal process con­ dition and closed when the process condition is abnormal. [ANSI/ISA-18.1-1979 (R1992)] field contact follower See auxiliary output

(auxiliary contact). field contact voltage Also known as trouble or signal contact voltage, the voltage that is applied to field contacts. [ANSI/ISA-18.1­ 1979 (R1992)] field curvature The form of an image that lies on a curved surface rather than a flat plane.

For single- and double-element lenses, cur­ vature is always inward, but for other types the curvature can be in either direction. field devices Equipment that is connected to the field side of the safety instrumented sys­ tem's I/O terminals. Such equipment includes field wiring, sensors, final control elements, and those operator interface devices that are hardwired to the I/O termi­ nals of safety instrumented systems. [ANSI/ ISA-84.01-1996] field-effect transistor (FET) A semiconduc­ tor device that has a conducting channel whose resistance is modified by the electro­ static field that is produced by an adjacent gate electrode.

field emission The electron emission that is induced from an unheated metal surface when a strong electric field is applied to it. field emitter display (FED) A flat-panel dis­ play that works much like a CRT: it shoots electrons at colored phosphors (pixels) so as to create an image on screen. But rather than illuminate the phosphors with a single elec­ tron gun, a "flat cathode" chip is placed behind each phosphor, which allows a flat panel to be used in l.ieu of a bulky picture tube. . . :: .. field excitation Controlling the speed of a series-wound electric motor or a diesel-elec­ tric locomotive engine by changing the rela­ tionship between the armature current and the field strength. This is done either by using shunts to reduce field current or by using field taps. field/frame In NTSC (National Television System Committee) video development, each frame has two fields, one for every even scan line and the other for every odd scan line. So NTSC has 60 fields and 30 frames per second. field-free emission current The electron cur­ rent that flows from a cathode when the elec­ tric gradient at the cathode surface is zero. field-installable Nominally, a fiber-optic splice or cable is field installable if it can be mounted by technicians working in the field without a lab full of equipment at hand. field of view 1. Volume in space that is defined by an angular cone extending from the focal plane of an instrument or video screen. 2. The solid angle, or the angle in a specified plane, over which radiant energy incident on a transducer is measured within specified tolerances. [ISA-37.1-1975 (R1982)] field piping That piping that connects the control center to items external to it. [ISA­ RP60.9-1981] field-programmable Timers and counters that have user-programmable parameters such as time/count ranges and output sequences. Units are often programmed by miniature rocker switches located inside the timer or by jumper wires leading to different connection points. field-programmable logic array (FPLA) An array of logic gates that can be programmed by the user. field-replaceable unit Computer hardware modules that can be easily substituted with others. field weld A weld that is made at a construc­ tion or installation site as opposed to a weld made in a fabrication shop.

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filament / fillet weld filament A very fine single strand of metal wire, extruded plastic, or other material. filament winding The process of fabricating a composite structure by winding a continuous fiber reinforcement on a rotating core under tension. The reinforcement usually consists of a glass, boron, or silicon-carbide thread that was either previously impregnated with resin or was impregnated during winding. filament-wound structure A composite structure that is made by fabricating one or more structural elements through filament winding. They are then cured and assembled, or assembled first and then the entire structure cured. See filament winding. . filar micrometer An attachment for a microscope or telescope that consists of two parallel fine wires or knife edges in an eyepiece.

One of them is in a fixed position and the other can be moved so it is perpendicular to its length by means of a very accurate micrometer screw. Filar micrometers are used to make accurate measurements of t:near distances in the optical field of view.

Actual distances are determined by dividing the micrometer reading by the magnification of a microscope, although in some cases the micrometer scale is calibrated for direct readi ing at a specific magnification. : file 1. A collection of related records that is treated as a unit. 2. An organized structure that consists of an arbitrary number of records for storing information on a bulk storage device, for example, a disk, drum, core, or tape. file gap An interval of space or time that is associated with a file to indicate or signal the end of the file. Related to gap. file handling The manipulation of data files by various methods, generally involving reading, writing, and comparing. file name extension An addition to a computer file name that indicates the file type, such as .bat, .com, and so on. file server A digital mass storage device that can be accessed by several computers, thereby providing for the common sharing of stored data. file specification A name that uniquely identifies a file maintained by an operating system. A file specification generally consists of at least three components: a device name that identifies the volume on which the file is stored, a file name, and a file name extension.

In addition, depending on the system, a file specification can include a user file directory name, or UIC, and a version number.

201

file structured device A device on which data are organized into files. The device usually contains a directory of the files stored on it. file transfer access and management (FTAM) One of the application protocols specified by Manufacturing Automation Protocol (MAP) and Technical and Office Protocol (TOP). See Manufactl/ring Automation Protocol (MAP) arid Technical and Office Protoeol (TOP). . .' fille¡o comp-Qsite Aplastic.s material that is made of sh'ort-strand fibers or a granular solid that is mixed into thermoplastic or thermosetting resin prior to molding. filled-system thermometer Any of several devices that consist of a temperature-sensitive element (bulb), an element that is sensitive to changes in pressure or volume (Bourdon tube, bellows, or diaphragm), capindicating or recording illary tubing, and device. The bulb, capillary tube, and pressure- or volume-sensitive element are partly or completely filled with a fluid that changes its volume or pressure in a predictable manner with changes in temperature.

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filler 1. An inert material that is added to paper, resin, elastomers, and other materials to modify their properties or improve quality in end products. 2. A material that is used to fill holes, cracks, pores, and other surface defects before applying a decorative coating such as paint. 3. A metal or alloy that is deposited in a joint during welding, brazing, or soldering. It is usually referred to as "filler metal." fillet 1. A concave transition surface between two surfaces that meet at an angle. 2. A molding or corner piece that is placed at the junction of two perpendicular surfaces to lessen the likelihood of cracking. fillet weld A roughly triangular weld that joins two members along the intersection of two surfaces that are approximately perpendicular to each other.

I

I

filling material/final element

II

filling material Quartz or glass particles.

[ANSI/ISA-12.25.01-1998 (IEC 60079-05 Mod)] fill-in-the-blank programming language A nonprocedural programming language in which programs are developed by filling out data sheets for an existing program. Exam­ ples include BICEPS, PROSPRO, and CODIL. film 1. A flat, continuous sheet of thermo­ p,lastic resin or similar material that is extremely thin in relation to its width and length. 2. A very thin coating, deposit, or reaction product that completely covers the surface of a solid. filmogen The material or binder in paint that imparts continuity to the coating. film resistor A type of resistor that uses a thin layer of resistive 'material, which is deposited on the resistor's insulating core.

For low-power applications film resistors are more stable than composition resistors and smaller and less expensive than the more accurate wire-wound resistors. film strength 1. Generally, the resistance of a film to disruption. 2. In lubricants, a measure of their ability to maintain an unbroken film over surfaces under varying conditions of load and speed. filter [Comm] 1. In electronic, acoustic, and optical equipment, a device that allows sig­ nals of certain frequencies to pass, while rejecting signals that have frequencies in another range. 2. A device that is used in a fre­ quency transmission circuit to exclude unwanted frequencies and to keep the chan­ nels separate. 3. A device to suppress interfer­ ence, which would appear as noise. 4. An algorithm or circuit that reduces the noise and other unwanted elements of a signal.

[Camp] 5. In computing, a machine word that specifies which parts of another machine word are to be operated upon. Thus, a filter is the criterion for an external command. Synon­ ymous with mask. [Sci] 6. In scientific con­ texts, a porous material or structural element that is designed to allow fluids to pass through it while collecting and retaining sol­ ids of a certain particle size or larger. filter, bandpass A circuit that is tuned so as to pass all frequencies between certain points in the spectrum. filter, low-pass A circuit that is tuned so as to pass all frequencies lower than a speCified cutoff point. filter aid An inert powdery or granular mate­ rial, such as diatomaceous earth, fly ash, or sand, that is added to a liquid about to be fil­

teredo The result is the formation of a porous bed on the filter surface, which increases the rate and effectiveness of the filtering process. filter cake The solid or semisolid material that is retained on the surface of a filter after a liquid containing suspended solids has passed through. filter capacitor A capacitor that is used as an element of an electronic filter circuit. filter inductor .An iJ1ductor that is used as an element of aR electronic filter circuit. filtering Protectio'n from "background noise" that could alter or destroy data transmission. filter medium The portion of a filter or filtra­ tion system that actually performs the func­ tion of separating out the solid material. It may consist of metal or nonmetal screening, closely woven fabric, papEr, matted fibers, a granular bed, a porous ceramic cup or plate, or other porous component. fin 1. A thin, flat, or curved projecting plate that is typically used to stabilize a structure surrounded by flowing fluid or to provide an extended surface for improving convective or radiative heat transfer. 2. A defect that consists of a very thin projection of excess material at a corner, edge, or hole in a cast, forged, molded, or upset part, which must be removed before the part can be used. final control element 1. The device that directly controls the value of the manipu­ lated variable of a control loop. Often the final control element is a control valve.

[ANSI/ISA-5.1-1984 (R1992)] 2. The compo­ nent of a control system (such as a control valve) that directly regulates the flow of energy or material to or from the process.

[ANSI/ISA-77.44.01-2000] 3. An instrument that takes action to adjust the manipulated variable in a process. This action moves the value of the controlled variable back toward the set point. 4. The last system element that responds quantitatively to a control signal and performs the actual control action.

Examples include valves, solenoids, and ser­ vometers. 5. The device that exerts a direct influence on the process. final controlling element The element in a control system that directly changes the value of the manipulated variable. See ele­ ment,final controlling. final element Also, "final device" and "final control device." In process control, the last device in a control loop that causes change in the process, such as a valve, motor drive unit, silicon-controlled rectifier (SCR), sole­ noid, and the like.

202

final set point device / firetube boiler final set point device A component or assembly of components that provides input to the process voting logic for actuated equipment. (See IEEE Standard 60) Note: Examples of final actuation devices are bistables, relays, pressure switches, and level switches. [ISA-RP67.04.02-2000; ANSI/ISA67.04.01-2000] fine grinding 1. The mechanical reduction of a powdery material to a final size of at least100 m~sh, usually in a ball mill or similar' grinding apparatus. 2. In metallography <;>r abrasive finishing, the process of producing a surface finish of fine scratches by using an abrasive that has a particle size of 320 grits or smaller. fineness The purity of gold or silver expressed in parts per thousand. For instance, gold that has a fineness of 999.8 has only 0.02 percent, or 200 parts per million, of impurities by weight. fines 1. In a granular substance that has mixed particle sizes, fines are those particles that are smaller in size than the average particle. 2. Fine granular material that passes through a standard screen on which the coarser particles in the mixture are retained.

3. In a powdered metal, the portion that consists of particles that are smaller than a specified particle size. finger plate A plate that is used to restrict the upward motion of the diaphragm and prevent diaphragm extrusion into the bonnet cavity in the full-open position. [ANSI/ISA75.05.01-2000) finish 1. A chemical or other substance that is applied to the surface of virtually any solid material to protect it, alter its appearance, or modify its physical properties. 2. The degree of reflectivity of a lustrous material, especially metal. Finish is usually described by one of the following imprecise terms, listed in increasing order of luster and freedom from scratches: machined, ground brushed, matte, dull lustrous, bright, polished, and mirror. 3. Generally, the surface quality, condition, or appearance of a metal or plastic part. finished goods Final materials on which all processing and production is completed. Finished goods may no longer be under the domain of manufacturing operations and control. [ANSI/ISA-95.00.01-2000] finished-good waivers Approvals for deviation from normal product specifications.

[ANSI/ISA-95.00.01-2000]

203

finish grinding The final step in a grinding operation, which imparts the desired surface appearance, contour, and dimensions. finishing temperature In a rolling or forging operation, the metal temperature during the last reduction and sizing step, or the temperature at which hot working is completed. finite element analysis (FEA) A modeling technique for predicting dynamic behavior before any hardware is build.

FInt Fieldbus Int~rnatiooal; formed as the successor to Norwegiari'Fieldbus Consortium.

FIP Factory Instrumentation Protocol; a French national field bus standard (1 Mbs) for linking sensing actuators and controllers in automation systems; supported by over 125 European companies.

FIR Finite impulse response filter; in digital signal processing (OS?), filter that has output determined by its coefficients and previous inputs and is characterized by having linear phase rt;sponse; see fIR. fire assay Determining the metal content of an ore or other substance by using techniques involving high temperatures. firebox The equivalent of a furnace. A term usually used for the furnaces of locomotive boilers and similar types of boilers. fire crack A crack that starts on the heated side of a tube, shell, or header and is caused by excessive temperature stresses. fired-pressure vessel A vessel that contains a fluid under pressure, which is exposed to heat from the combustion of fuel. fire point The lowest temperature at which, under specified conditions, fuel oil gives off enough vapor to burn continuously when ignited. fireproof Resistant to combustion or to damage by fire under all but the most severe conditions. fire-resistant Resistant to combustion and to heat of standard intensity for a specified time without catching fire or failing structurally. fire retardant 1. Treated by coating or impregnation so that a combustible material-wood, paper, or textile, for instancecatches fire less readily and burns more slowly than untreated material. 2; The substance that is used to coat or impregnate a combustible material to reduce its tendency to burn. firetube A tube in a boiler that has water on the outside and carries the products of combustiun on the inside. firetube boiler A boiler that consists of straight tubes that are surrounded by water

firewall technology / fixed point and steam and through which the products of combustion pass. firewall technology In computer-based networks, the methods for protecting databases and files from being improperly accessed through open networks such as the Internet. firewire Computer network technology that permits several electronic devices to communicate. It is made up of six individual cables: one for power, one for ground, two for data, pf\d.t\Yo for strobe, which synchronize the data. Its assembly is shielded. firing-rate control A pressure, temperature or flow controller that controls the firing rate of a burner according to pressure or temperature deviation from set point. The system may be arranged so it operates the burner on-off, high-low, or in proportion to load demand. firmware Special-purpose memory units that contain software embedded in protected memory, which is required for the operation of programmable electronics. [ANSl/ISA84.01-1996] first alert See first Ollt (first alert). first in, first out (FIFO) An ordered queue. A discipline in which the first transaction to enter a queue is also the first to leave it. Contrast with last in,first out (LIFO). first-level address See direct address. first-order system A system that is definable by a first-order differential equation. first out (first alert) A sequence feature that indicates which of a group of alarm points operated first. [ANSl/ISA-18.1-1979 (R1992)] first out reset See reset.

FIS Financial Information System; a computer database of customer and vendor accounts used in EIS. See ÂŁ1S. Fisher loop test One of several Wheatstone bridge test arrangements that is commonly used to determine the distance to a fault (grounded or crossed wires) in a communications cable. fish eye 1. An area on a fracture surface that has a characteristically white crystalline appearance, usually because of internal hydrogen cracking. 2. A small globular mass in a blended material such as plastic or glass that is not completely homogeneous with the surrounding material. Fisheye is particularly noticeable in transparent or translucent materials. fishing tool An elongated or telescoping tool that has a magnet, hook, or grapple at one end. It is used to retrieve objects from inaccessible places. fish plate Either of the two plates that are bolted or riveted to the webs of abutting rails

or to beams on opposite sides so as to secure a mechanical joint. fishtail Excess metal at the trailing end of an extrusion or a rolled billet or bar. It is generally cropped and is either discarded or recycled into a melting operation. fissure A small, cracklike surface discontinuity, often one whose sides are slightly opened or displaced with respect to each other. fit The closeness of mating parts in an assembly as determined-by their respective dimensions and tolerances. Fits may be classified as running (sliding) fits, locational fits, transition fits, or force (shrink) fits, depending on the size and direction of the dimensional allowance (it is positive for running fits or negative for force fits). Fits may also be termed" clearance fits" or "interference fits" if there is always a gap between the mating parts or always interference, respectively, as long as the parts are within specified tolerances.â&#x20AC;˘â&#x20AC;˘'. ' . ,~ , fitting An aUXiliary part of standard size and configuration that can be used to facilitate assembly. In constructing a system of pipe or tubing, for example, connections are more easily made if standard elbows, tees, unions, and couplings are used to connect straight lengths of pipe, rather than bending the pipe or making special preparations before welding lengths of pipe together. fixed carbon In making the proximate analysis of a solid fuel, fixed carbon is the carbonaceous residue, less the ash remaining in the test container, after the volatile matter has been driven off. fixed equipment Equipment that is fastened to a support or otherwise secured in a specific location. [ANSl/ISA-82.02.01-1999 (IEC 1010-1 Mod)] fixed-length record A record in which the number of characters is constant. fixed palette In the context of the Internet, an established color palette on a Web browser that converts graphic images into its own colors, rather than converting the colors from the original image. fixed pitch A typeface in which all the letters are the same wid tho fixed point 1. A reproducible standard value that is usually derived from a physical property of a pure substance. It can be used to standardize a measurement or check an instrument calibration. 2. Pertaining to a numeration system in which the position of the radix point is fixed with respect to one end of the numerals, according to some convention. See fixed-point arithmetic.

204

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fixed-point arithmetic 1. A method of calculation in which operations take place in an invariant manner, and in which the computer does not consider the location of the radix point. This is illustrated by desk calculators or slide rules that require the operator to keep track of the decimal point, and also by many automatic computers, in which determining the location of the radix point is the programmer's responsibility. Contrast with floating-point arithmetic. 2. A type of arithmetic in which the operands and results of all arithmetic operations must be properly scaled so they'have a magnitude that falls between certain fixed values. fixed-point data In data processing, the representation of information by means of the set of positive and negatiye integers. It is faster than floating-point 'data and requires fewer circuits to implement. fixed-point notation In data processing, numbers that are expressed by a set of digits that have the decimal point in the correct position. fixed-point part In a floating-point representation, the numeral in a pair of numerals that represents the fixed-point factor by which the power is multiplied. Synonymous with

used to tell some later part of a program that some condition occurred earlier. 3. An indicator that is used to identify the members of several intermixed sets. 4. A storage bit whose location is usually reserved to indicate the occurrence or nonoccurrence of some condition. For example, a Halt/Run flag would be 1 when the processor was halted and 0 when in the Run condition. flag register An. eigh.t-bit register in which each bit acts as a flag:' :.t-;..l flake 1. A dry, unpbsticized, cellulosic, plastics base material. 2. A plastics material in chip form that is used as feed in a molding operation. 3. An internal hydrogen crack such as may be formed in steel during cooling from high temperature. Also known as fisheye, "shattercrack," or "snowflake." 4.

Metal powder)n ,the form of fish-scale particles. Also known as "flaked powder." flame A luminous body of burning gas or vapor. flame detector A device that indicates whether fuel (for example, liquid, gaseous, or pulverized, is burning, or if ignition has been lost. The indication may be transmitted to a signal or to a control system. flame hardening A form of surface hardening that uses the inherent hardenability of a steel or other hardenable alloy to produce a hardened surface layer by spot-heating the metal with a fuel-gas flame to a shallow depth and then rapidly cooling the heated metal. flame photometer An instrument for determining compositions of solutions by spectral analysis of the light emitted when the solution is sprayed into a flame. flame plate A baffle of metal or other material for directing gases of combustion. flame propagation rate Speed of travel of ignition through a combustible mixture enclosure's joints or structural openings. This type of protection is referred to as "d". See also explosion-proof enclOSllre. [ANSI/ISA-12.01.011999] flameproof enclosure 1. An international term that describes an enclosure that can withstand the pressure that develops during an internal explosion of an explosive mixture. It also prevents the explosion from being transmitted to the explosive atmosphere surrounding the enclosure. It operates at such an external temperature that an explosive gas or vapor surrounding it will not be ignited by the internal explosion. This enclosure is similar to an explosion-proofenclosure and is referred to by IEC as "Ex d". [IEC 12.1]2. A type of protec-

"mantissa." fixed-program computer A computer in which the sequence of instructions is permanently stored or wired in. The instructions perform automatically and are not subject to change either by the computer or the programmer, except by rewiring or changing the storage input. Related to wired-program com-

puter. fixed restrictor A fixed, physical restriction to fluid flow. fixed storage A storage device that stores data that cannot be altered by computer instructions. An example of fixed storage is magnetic core storage with a lockout feature, or a photographic disk. fixed word length Having the property of a machine word, which always contains the same number of characters or bits. fixture 1. An auxiliary component or operator aid that is attached to a structure or machine enclosure-a light or tool shelf, for instance. 2. A special holder that positions the work in a machining operation but does not guide the tool.

FL Fail locked; default mode of the final element in process, typically a valve. flag 1. A bit of information that is attached to a character or word to indicate the boundary of a field. 2. An indicator that is frequently

205

flameproof joint / flangeless control valve tion for electrical apparatuses in which the enclosure will withstand the internal explosion of a flammable mixture that has penetrated into the interior. It is designed so that an external explosive atmosphere consisting of one or more of the gases or vapors for which it is designed will cause no damage and ignite no flame through any of the enclosure's joints or structural openings. Note: This type of protection is indicated by the letter "du. [ANSI/ISA-12.22.01-1998 (IEC 60079-1 Mod)] flameproof joint The place where corresponding surfaces of the different parts of a flameproof enclosure (or the conjunction of enclosures) come together, and where flame or the products of combustion may be transmitted from the inside to the outside of the enclosure. [ANSI/ISA-'l2.22.01-1998 (IEC 791 Mod)] flame spraying 1. The process of applying a plastic coating on a surface by projecting finely powdered plastic material, mixed with suitable fluxes, through a cone of flame toward the target surface. 2. Thermal spraying by feeding an alloy or ceramic coating material into an oxyfuel-gas flame. Compressed gas mayor may not be used to atomize the molten material and propel it onto the target surface. flame-spray strain gauge A fine-wire strain gauge element that is attached to a substrate by flame-spraying a ceramic encapsulation over the element, which damages neither the gauge nor the substrate. This attachment technique produces a bond that is suitable for ?perati~g over the temf'erature range 270 to 820 C (-450 to 1,500 F). flame treating Making inert thermoplastics parts receptive to inks, lacquers, paints, or adhesives by bathing them in open flames so as to promote surface oxidation. flammability Susceptibility to combustion. flammable (explosive> limits Of a gas or vapor, the lower and upper flammable (explosive) limit (LFL/LEL and UFL/UEL, respectively) percentages by volume of the concentration of gas in a gas-air mixture that will form an ignitable mixture. Note 1: For additional information, refer to NFPA 325 and IEC 60079-20. Note 2: The term explosive as it relates to atmospheres and mixtures is in the process of being replaced with the more technically correct term flammable throughout many national and international standards. This dictionary, however, continues to use the term explosive in many definitions because those definitions have been derived

from documents yet to be updated. [ANSI/ ISA-12.01.01-1999; ISA-RP12.4-1996] flammable gas or vapor A gas or vapor that, when mixed with air in certain proportions, will form an explosive gas atmosphere.

[ANSI/ISA-12.01.01-1999] flammable liquid 1. A liquid, usually a liquid hydrocarbon, that gives off combustible vapors. 2. Any liquid that has a flash point below 37.8 °C (100°F) and a vapor pressure that d~es not exceed)?5 kPa (40 psia) at 37.8 °C (100 OF). Note: Fo.r·additional information, refer to NFPA 325. [ANSI/ISA-12.01.01-1999] flammable range The tange of flammable vapor concentrations or gas-air mixtures in which flame will propagate when it contacts a source of ignition. [ANSI/ISA-12.13.012000] LCWE~

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Flammable Range and Limits flanged Valve end connections that incorporate flanges that mate with corresponding flanges on the piping. There are four basic types: split camp, threaded, welded, and end-toend dimension. (1) Split clamp: valve end connections of various proprietary designs that use split clamps to apply gasket or mating surface loading. (2) Threaded: valve end connections that incorporate threads, either male or female. (3) Welded: valve end connections that have been prepared for welding to the line pipe or other fittings. May be further divided into butt weld (BWE) or socket weld (SWE). (4) End-to-end dimension: A nonstandard control valve term. See face-to-face dimension. [ANSI/ISA-75.05.01-2000] flanged body A valve body with full-flanged end connections. [ANSI/lSA-75.05.01-2000] flanged ends Valve end connections that incorporate flanges, which make possible pressure seals by mating with corresponding flanges on the piping. [ANSI/ISA-75.05.012000] flange facing The finish on the end connection that mates with the gasket surfaces.

[ANSI/ISA-75.05.01-2000] flangeless control valve A valve without integral line flanges. It is installed by bolting

206

flange-retained liner / flexible function block between companion flanges and has a set of bolts, or studs, that generally extend through the companion flanges. [ANSI/ISA-75.05.012000] flange-retained liner A liner that is retained in the body of a butterfly valve by the pipe flanges or by a continuous or segmented ring. The segmented ring provides a way to adjust the liner to disk interference so as to achieve improved sealing. The bore of the pipe. flanges is smaller in diameter than the body bore. Therefore, the flanges retain the liner in the body. [ANSI/ISA-75.05.01-2000] flange taps See orifice flange taps. flank 1. On a cutting tool, the end surface that is adjacent to the cutting edge. 2. On a screw thread, the side of the thread. flap valve A valve with a hinged flap or disk that swings in only one direction. flareback A burst of flame from a furnace in a direction that is opposed to the normal flow. It is usually caused by the ignition of an accumulation of combustible gases. flared tube end The projecting end of a rolled tube that is expanded or rolled into a conical shape. flaring Increasing the diameter at the end of a pipe or tube in order to form a conical section. flash 1. In plastics molding, elastomer molding, or metal die casting, a portion of the molded material that overflows the cavity at the mold parting line. 2. A fin of material that is attached to a molded, cast or die-forged part along the parting line between die halves. It may also be attached to a resistance flash-welded, upset-welded, or frictionwelded part along the weld line. flash converter A converter in which all bit choices are made at the same time. flasher A device that causes visual displays to turn on and off repeatedly. Common types of flashing include fast flashing, flashing, slow flashing, and intermittent flashing.

[ANSI/ISA-18.1-1979 (R1992)] flashing 1. Steam that is produced by discharging water at saturation temperature into a region of lower pressure. 2. A flow condition in which vapor pockets formed inside a valve persist downstream of the valve because the valve outlet pressure is at or below the fluid vapor pressure. [lSARP75.23-1995] flashlamp A gas-filled lamp that emits a short, bright flash of light when it is excited by an electrical pulse passing through it. A broad range of wavelengths are produced,

and their precise nature depends on the gas or gases used. flash line A raised line on the surface of a molded or die cast part that corresponds to the parting line between mold faces. flash memory One of the first applications of PCMCIA cards. A Type I card (see PCMCIA) that contains up to 20 MB RAM and a small battery so memory is retained when unplugged. Flash me.mory is an alternative to floppy disks and much faster than either .floppy or hard disks. flashover A disruptive:discharge in the form of arc or spark between two electrical conductors or between conductor and earth (ground). . flash plating - The electrodeposition of a very thin film of metal, usually just barely enough to completely cover the surface. flash point. T.he minimum temperature at which a liquid giv~s off vapor in sufficient concentration to form an ignitable mixture with the air near the surface of the liquid, as specified by a test. Note: For additional information, refer to NFPA 325. [ANSI/ISA12.01.01-1999] flatbed scanner A "device that scans images much as photocopy machines do; the original art or document is positioned face down on glass plate. flattening Straightening a metal sheet by passing it through a set of staggered and opposing rollers. These rollers bend the sheet slightly to flatten it, without reducing its thickness. flattening test A test that evaluates the ductility, formability, and weld quality of metal tubing by flattening it between parallel plates to a specified height. flatting agent A chemical additive that promotes a nonglossy, matte finish in paints and varnishes. flat tuning Tuning that has substantially equal response to the range of frequencies. flaw A discontinuity or other physical attribute in a material that exceeds acceptable limits. Since the term flaw is nonspecific, more specific terms such as defect, discontinuity, or imperfection are often preferred. flexible coupling A device that connects the shafts of the driver and driven machines and is at the same time capable of being bent and strong enough to transfer the power. Semiflexible coupling is a better term. flexible function block Similar to a standard function block, except that the function of the block, the order and definition of the block parameters, and the time required to execute

207

flexible lip seal! floating plug the block are determined by an applicationspecific algorithm that is created by a programming tool. Flexible function blocks (FBs) are typically used to control discrete processes and hybrid (batch) processes. A programmable logic controller (PLC) can be modeled as a flexible function block device.

See standard function block and programmable

float that rides up and down with liquid level. Contrast with floating control. float gauge Any of several types of devices that use pulleys, levers, or other mechanisms to transmit the position of a float to a scale that indicates liquid level in a tank or vessel.

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[ANSI/ISA-75.05.01-2000] flexible manufacturing system (FMS) A manufacturing system under computer control that provides automatic material handling. The system is primarily deSigned for batch manufacturing. flexivity The temperature rate of flexure for a bimetal strip of given dimensions and material composition. flicker The flashing effect of a video screen as the electron beam that creates the image follows its raster pattern. See raster. flight monitor package A special software system that enables several operators to monitor data from an aircraft or other source in rFill time. flinchmg In quality control inspection, the failure of an inspector to call a borderline defect a defect. flint glass An optical glass that contains lead or other elements that raise its refractive index between 1.6 and 1.9, that is, higher than other types of optical glass. flip-flop 1. A bistable device, that is, a device that is capable of assuming two stable states.

2. A bistable device that may assume a given stable state, depending on the history of pulses of one or more input points. Flip-flops also have one or more output points and are capable of storing one bit of information. 3. A control device for opening or closing gates, that is, a toggle. float 1. Any component that has positive buoyancy. For example, a hollow watertight body that rests on the surface of a liquid, partly or completely supported by buoyant forces. [Cant] 2. In control, the amount of time between the completion of a task or activity and the start of the next. float chamber A vessel in which a float regulates the liquid level. float control A type of control apparatus in which the control signal is regulated by a .楼

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[ANSI/ISA-75.05.01-2000] floating control A control device in which the au tpu t control signal is proportional to the difference between an indicator signal and the controller's set point. This difference is often referred to as an "error signal." In operation, tloating control reduces the tendency to overshoot the set point because it reduces power input to the system as the controlled variable approaches the set point value. Contrast with float control. floating control action See control action,

floating. floating controller See controller, floating. floating control mode A controller mode in which an error in the controlled variable causes the output of the controller to change at a constant rate. The error must exceed preset limits before controller change starts. floating-gate PROM Optically erasable readonly memory. floating plug A short-nosed mandrel that is attached to a rod, which is inserted into pipe or tubing during reduction by drawing. Also known as "plug die."

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floating point 1. An arithmetic notation in which the decimal point can be manipulated.

The values are sign, magnitude, and exponent (+.833 x 102). Contrast with fixed point. 2. A form of number representation in which quantities are represented by a bounded number (mantissa) and a scale factor (characteristic or exponent). The scale factor consists of a power of the number base, for example, 127.6 = 0.1276'10"3, where the bounds are 0 and 1 for the mantissa, and the base is ten. floating-point arithmetic' A method of calculation that automatically accounts for the location of the radix point. This usually is accomplished by handling the number as a signed mantissa multiplied by the radix, raised to an integral exponent. For example the decimal number +88.3 might be written as +0.883'10"2, the binary number -0.0011 as -0.11'2*'-2. Contrast with fixed-point arithmetic.

See radix point. floating-point base In floating-point representation, the fixed positive integer that is the understood base of the power. Synonymous with floating-point radix. floating-point routine A set of subroutines that causes a computer to execute floating-point arithmetic. These routines may be used to simulate floating-point operations on a computer that has no built-in floating-point hardware. floating rate The rate of motion of the final control element in a proportional-speed floating-control system, which corresponds to a given deviation. floating speed The rate of motion of the final control element in a single-speed or multispeed floating-control system. floatless level control Any device for measuring or controlling liquid level in a tank or vessel without the use of a float. Such devices include manometers, electrical probes, capacitance devices, radiation instruments, and sonic or ultrasonic instruments. float switch An on-off switch that is activated by the position of a float. float valve An on-off-type valve whose action is triggered by the rise or fall of a floa t. flooding The consequence of the excessive loading of distillation column liquid. In effect, the liquid on trays becomes too deep for the vapor to pass through, or the vapor flow rate is too high. This creates an excessive differential pressure or a decrease in the differential temperature across the column. floppy disk A flexible plastic disk that is coated with magnetic oxide and used for data entry to a computer. A slot in the disk's

209

protective envelope or housing, which remains stationary while the disk rotates, exposes the track positions for the magnetic read/write head of the drive unit. Also known as a diskette. flotation A process for separating particulate matter in which differences in surface chemical properties are used to make one group of particles float on water while other particles do not. Flotation is primarily used to separate minerals frpm gangue, but it is also used in some chemical and biological processes flow [Eng] 1. In engineering, the rate of flow of a liquid is expressed in volume units per unit of time. Examples include meter 3 /second (m 3 /s). [ISA-RP31.1-1977] 2. The movement of material in any direction. [Comp] 3. In computing, the order of events in the computer's solutiOJ;rt~ a problem. flowability A general term that describes the ability of a slurry, plasticized material, or semisolid to behave like a fluid. flow brazing A brazing process in which the joint is heated by pouring hot molten nonferrous filler metal over the assembled parts until the brazing temperature is attained. flow cases Known conditions of flow. flow characteristic An indefinite term. The preferred terms are inherent flow characteristic and installed flow characteristic. [ANSI/ISA75.05.01-2000] flowchart 1. A system analysis tool that provides a graphical presentation of a procedure. It includes block diagrams, routine sequence diagrams, general flow symbols, and so forth. 2. A chart to represent, for a problem, the flow of data, procedures, growth, equipment, methods, documents, machine instructions, and the like. 3. A graphical representation of a sequence of operations that uses symbols to represent the operations such as Compute, Substitute, Compare, Jump, Copy, Read, Write, and so on. 4. The graphical representation of the steps performed in a process. 5. The sequence of logic operations that are implemented in hardware, software, firmware, or manual procedures. flow coat To apply a coating by pouring liquid over an object and allowing the-excess to drain off. flow coefficient (C v , K v ) A constant that establishes flow capacity. It is related to the geometry of a valve for a given valve travel.

[ANSI/ISA-75.05.01-2000] flow coefficient A constant (C v ) that can be used to predict flow rate for a given valve opening. It is related to the geometry of a

I

flow compensation / flow rate range valve. See ANSI/ISA-75.01-2000, "Control Valve Sizing Eqllations," and ANSI/ISA75.02-1996, "Control Valve Capacity Test Procedure." [ANSI/ISA-75.11-1985 (R1997)] flow compensation Using secondary signals to correct flow values for changes in density or viscosity. flow control [Eng] 1. In engineering, any method for controlling the flo\v of a material through piping, ductwor~, or channels.

[Camp] 2. In computing, a procedu~ for regulating the flow of data once the buffer of a specific dev!ce has reached capacity. flow-control orifice The part of the flow passageway that, along with t11e closure member, modifies the rate of flow through the valve. The orifice may be provided with a seating surface to prov~de tight shutoff or limited leakage. This seating surface is to be contacted by or closely fitted to the closure member. [ISA-75.03-1992] flow diagram See j1ozvchart. flow line 1. The connecting line or arrow between symbols on a flowchart. 2. A mark on a molded plastic part where two flow fronts met during molding. Also known as "weld mark." 3. In mechanical metallurgy, a path followed by minute volumes of metal during forming. 4. A texture line, often revealed by etching a surface or section, that indicates the direction of metal flovv during hot or cold working. flow marks Wavy surface marks on a molded thermoplastic part resulting from the improper flow of resin during molding. flowmeter 1. A device that measures the rate of flow or quantity of a moving fluid in an open or closed conduit. It usually consists of both a primary and a secondary device.

Note: It is acceptable in practice to further identify the flowmeter by its applied theory, as "differential pressure," "velocity," "area," "force," and so on, or by its applied technology, as "orifice," "tllrbine," "vortex," "ultrasonic," and the like. Examples of flowmeters include the turbine flowmeter, magnetic flowmeter, fluidic pressllre flowmeter, and so on. 2. An instrument that is used to measure the linear, nonlinear, mass, or volumetric flow rate or to measure the discharge rate of a fluid flowing in a pipe. Also kno\vn as a "fluid meter." flowmeter primary device The device that is mounted internally or externally to the fluid conduit. It produces a signal that has a defined relationship to the fluid flow in accordance with knovvn physical laws that relate the interaction of the fluid to the pres-

MAGNETIC FIELD

Electrol1'Iagnetic FlolUlneter

ence of the"pr.imary device. Note: The primary device may consist of one or more elements that are necessary to produce the primary device signal. [ANSI/ISA-51.1-1979 (R1993)] flowmeter secondary device The device. tha~路.~i):~ l responds to the signal from the primary .. ~. ", . device and converts it into a display or into an output signal that can be translated relative to flow rate or quantity. Note: The secondary device may consist of one or more elements that are needed to translate the primary device signal into standardized on nonstandardized display or transmitted units. [ANSI/ISA-51.1-1979 (R1993)] flow mixer A device for mixing two solids, liqllids, or gases together, in which the mixing action occurs as the materials pass throllgh the device. Also known as a "line mixer." flow nozzle A type of differential pressureproducing element that has a contoured entrance. It is characterized by its ability to be mounted between flanges and to have a lower permanent pressure loss tllan an orifice plate. flow rate 1. The actual speed or velocity of flow movement. 2. The time rate of motion of a fluid (usually contained in a pipe or duct), expressed as fluid quantity per unit time.

[ISA-37.1-1975 (R1982)] 2. The quantity of flllid that moves through a pipe or channel within a given period of time. flow rate instability (bistable ~Jow) An abrupt change in the control valve flow rate, which OCCllrs independent of changes in valve position. It may be caused by variable wall attachment of the fluid stream at the valve orifice, by flashing, or by cavitation. flow rate range The range of flow rates, bounded by the minimllm and maximum flow rates.

210

flow separation / fluorescence flow separation A flow condition in which the fluid boundary layer flows away from the boundary wall instead of flowing along it. A turbulent wake exists downstream of the point of flow separation, which is characterized by the presence of vortices. These vortices contain regions of high local fluid velocities and hence low, local pressures. The areas of low pressure are potential sites for vapor formation. [ISA-RP75.23-1995] . flow soldering See wave soldering. flow straightener A supplementary length of straight pipe or tube. It contains straightening vanes or the equivalent and is installed directly upstream of the turbine flowmeter for the purpose of eliminating swirl from the fluid entering the flowmeter. [ISA-RP31.11977] flow transmitter A device; that senses the flow of liquids in a pipe and converts the sensor output into electric signals that are proportional to the flow rate. These signals can be transmitted to a remote indicator or controller. flue A conduit or duct for conveying combustion products from a furnace chamber or firebox to the point of discharge into the atmosphere. flue dust The particles of gas-borne solid matter carried in the products of combustion. flue gas The gaseous products of combustion in the flue to the stack. [ISA-77.41-1992] flue-gas analyzer An instrument that monitors the composition of flue gas as it passes out of a boiler or heating unit. The readout is used to guide the adjustment of combustion controls so as to achieve maximum combustion efficiency or heat output.

fluid coupling A device for transmitting rotational motion and power between shafts by means of the acceleration or deceleration of oil or another suitable liquid. Also known as "hydraulic coupling." fluidics The technology of using fluid dynamics to perform sensing, control, data acquisition, information processing, and device actuation functions, without relying on moving mechanical parts (see the illustration of a fluidicilowm.~t.er). .

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Fluidic Flowmeter (Coanda Effect) fluidity The degree to which a substance flows freely. fluidized bed A dynamic mixture of a gas and/ or vapor and solid particles so minute that the mixture resembles a fluid in motion. fluid meter See flowmeter. fluid motor-type valve A fluid-powered device that uses a rotary motor to position the actuator stem. [ANSI/ISA-75.05.01-2000] flume An adaptation of the venturi concept of flow constriction applied in this case to open-channel flow measurement. See venturi.

1 1 1 CElLAPPROX. 1500 OF

In Situ Flue Gas Analysis Flume

fluid A gas or liquid that has the property of undergoing continuous deformation when it is subjected to any finite shear stress, for as long as the shear stress is maintained.

fluorescence 1. The emission of electromagnetic radiation from a surface when it absorbs energy from other electromagnetic or particulate radiation. The emission is sus-

211

fluorescence spectroscopy / FM tained only so long as the stimulating radia­ tion impinges on the material. 2. The electromagnetic radiation produced by the process described in definition 1. 3. Charac­ teristic X-rays that are produced because of the absorption of higher-energy X-rays. fluorescence spectroscopy The study of materials by the light they emit when irradi­ ated by other light. Many materials emit visi­ ble light after they have been illuminated by ultraviolet light. The intensity and wave­ lengtl1s of the emitted light can be used to identify the material and its concentration. fluorometer "An instrument for measuring the fluorescent radiation that is emitted by a material when excited by monochromatic incident radiation. That radiation is usually filtered radiation from a mercury arc lamp or from a tungsten or molybdenum x-ray tube.

Also spelled" fluorimeter." fluoroplastics A family of plastics resins that is based on the fluorine substitution of hydrogen atoms in certain hydrocarbon mol­ ecules. fluoroscopy X-ray examination that is similar to radiography, but in which the image is produced on a fluorescent screen instead of on radiographic film. flush 1. The injecting of a fluid into the sam­ ple line where the flow of sample fluid can be directed to a portable container. It may sometimes be referred to as "sample point."

2. The injection of a fluid into the line at an upstream point in order to remove line fluid from the downstream line. [ANSI/lSA­ 67.02.01-1999] flushing Removing debris, deposits, wear particles, or used lubricating oil from a pip­ ing system, chamber, or mechanism by circu­ lating a liquid such as a solvent oil or water, then draining the system to carry off unwanted substances. flushing connection A connection on the instrument, manifold, or piping to permit the periodic backflow of an external fluid for clearing purposes. flush left (right) In the typographical compo­ sition of screen displays and printing, setting the lines of type so they line up vertically at the left (or right) margin. In other words, the alignment of type so that the left start point (or right-side end point) for each line is the same. Most books are typeset so the lines are flush both left and right. flush paragraph In the typographical compo­ sition of screen displays and printing, a para­ graph with no indentation.

fluted-rotor flowmeter A type of flow-mea­ surement device in which fluid is trapped between two fluted rotors that are dynami­ cally balanced but hydraulically unbalanced.

This causes them to turn at a rate that is pro­ portional to the volume rate of fluid flow. fl utter 1. In tape recorders, the higher-fre­ quency variations in record and / or repro­ duce speed that cause time-base errors in the record/reproduce process. 2. The irregular alternating motion of a control surface, often because of turbulence ina fluid flowing past it. 3. Repeated speed variations in computer processing. flux 1. In metal refining, a substance that is added to the melt to remove undesirable substances such as sand, dirt, or ash. It is sometimes added to absorb undesirable ele­ ments or compounds such as sulfur in steel­ making or iron oxide in copper refining. 2. In welding, brazing, and soldering, a substance that is preplaced in the joint or fed into the molten zone so as to prevent oxides or other undesirable compounds from forming, or to dissolve them and make it easy to remove them. 3. In magnetic or electromagnetic applications, the integral of magnetic field strength over the cross-sectional area of the field. flux gate A detector that produces an electric signal whose magnitude and phase are pro­ portional to the magnitude and direction of an external magnetic field that is aligned with the detector's axis. flux guide A shaped piece of metal that is used in magnetic or electromagnetic applica­ tions to direct magnetic flux along preferred paths or to prevent it from spreading beyond specific boundaries. fluxmeter An instrument for measuring the intensity of magnetic flux. fly A fan with two or more blades that is used in timepieces or light machinery to con­ trol rotational speed by means of air resis­ tance. flying lead A wire lead that exits in the back of the connector hood on the outside of the cable jacket. It is normally attached to the drain wire or shield and then connected to the chassis of the switch, modem, and so on.

Also called hardware control lead. flywheel A balanced rotating element attached to a shaft which utilizes inertial forces to maintain uniform rotational speed and damp out small variations in power gen­ erated by the driving elements.

FM Factory Mutual Research Corporation; organization that sets industrial safety stan­

212

FM / folding error dards, generally to protect the process; focused on fire safety and prevention. They test and approve products, and FM approval is recognized by OSHA as indicating a prod­ uct that does not create a fire hazard. Com­ pare with UL. Also frequency modulation; a method of transmission in which the carrier frequency varies in accordance with the sig­ nal.

FM Seefreqllency modulation.

FM discriminator A device that converts fre­ quency variations into proportional varia­ tions in voltage or current transmission frequency range into narrower banks, each of which is used for a separate channel.

FMEA Failure mode and effects analysis; a procedure by which every individual com­ ponent is ranked with percentage failure val­ ues for each failure mode (i:e.; transistor short, open, drift, etc.) so as to determine their respective failures in time (FIT). Then, an overall impact is calculated for the device in which all of these components are used; used in developing MTTF. See MTTF. FM/FM The frequen~y modulation of a car­ rier by subcarriers that are frequency modu­ lated by information.

FM (tape record/reproduce) The tape record/reproduce process whereby data , modulate an FM oscillator for recording and are demodulated by an FM discriminator.

F number The ratio of the principal length of a lens to its diameter.

FO Fail open; default mode of the final ele­ ment in the process, typically a valve. foaming 1. Any of various methods for intro­ ducing air or gas into a liquid or solid mate­ rial so as to produce a foam. 2. The contin­ uous formation of bubbles that have suffi­ ciently high surface tension to remain bub­ bles beyond the disengaging surface. foam-in-place A method that is widely used to apply foamed insulation to homes and industrial equipment. Two or more reactive substances are deposited onto a surface where the foaming reaction takes place. focal length The distance from the focal point of a lens or lens system to a reference plane at the lens's location, measured along the focal axis of the lens system. focal point 1. The location on the opposite side of a lens or lens system where rays of light from a distant object meet at a point.

Also known as focus. 2. The point in space where a beam of electromagnetic energy (such as light, X-rays, or laser energy) or of particles (such as electrons) has its greatest concentration of energy. It corresponds to the

point where a converging beam of energy

undergoes a transition to become a diverging

beam.

focal spot The area of the target in an X-ray

tube where the stream of electrons from the

cathode strikes the target.

focus 1. To adjust the position of a lens with

respect to an imaging surface so that sharp

features of the object appear sharp in the

image. 2. A focal pOint. focusing. coil An .assembly tha tcontains one Qr more.el~ctrom.agnetic·.coilsto focus an electron beam. focusing electrode An electrode that is con­

figured so that its electric field acts to control

the cross-sectional area of an electron beam. focusing magnet An assembly that contains one or more permanent magnets or electro­ magnets and is used to focus an electron beam.

FOF First out fault; system to determine accurately the sequepce of alarms in a pro­ cess or plant. fog A defect in developed radiographic, pho­ tographic, or spectrographic emulsions that consists of uniform blackening, caused by unintentional exposure to low-intensity light or penetrating radiation. fogged metal A metal surface whose luster has been greatly reduced by the creation of a film of oxide or other reaction products. fog quenching Rapidly cooling an item by subjecting it to a fine mist, usually of water. foil A very thin metal sheet, usually less than 0.006 in. (0.15 mm) thick. foil strain gauge A type of metallic strain gauge. It is usually made in the form of a back-and-forth grid by photoetching a pre­ cise pattern on foil made of a special alloy that has high resistivity and a low tempera­ ture coefficient of resistivity.

FOIRL Fiber-Optic Inter Repeater Link; early implementation of subset of IEEE 802.3 10BASE FL standard designed to connect fiber-optic repeaters at 10Mbps. Used by var­ ious Ethernet manufacturers to produce net­ work and port interface cards as well as MAUs/transceivers. foldback In the current-limiting circuit of a power supply, the ability to reestabHsh a flow of current after overload has caused the interruption of current flow by exceeding the preset limits. folding error An error in sampling an elec­ tronic signal that arises from the failure to sample at a high enough rate (sampling rate should be at least double the maximum sig­ nal frequency). The result is that the sam­

213

I

foldover / fore vacuum

II

pIing device perceives high-frequency components of the signal as low-frequency components. Also known as aliasing error. foldover A device characteristic that is exhib­ ited when a further change in the input pro­ duces an output signal that reverses its direction from the specified input-output relationship. [ANSI/ISA-67.04.01-2000] folio In the typographical composition of screen displays and printing, another name for the page number. font The complete assortment of typesetting characters (letters, numbers, punctuation marks, etc.) of a particular style. foot A fundamental unit of length in the Brit­ ish and U.s. customary systems of measure­ ment that equals 12 inches. footlamberts The unit of brightness in video displays. foot-pound A force of one pound applied to a lever that is one foot long. forceback A back-calculation within the algo­ rithm function block to prevent signal "bump" during multitasking (i.e., switching between functions). Forceback is particu­ larly important in linking cascaded process control loops in microprocessor-based con­ trollers. force factor 1. The complex ratio of the force that is required to block the mechanical sys­ tem of an electromechanical transducer and the corresponding current in the electrical system. 2. The complex ratio of the open-cir­ cuit voltage in the electrical system of an electromechanical transducer and the corre­ sponding velocity in the mechanical system. force feedback A method of error detection in which the force exerted on the end ele­ ment is sensed and fed back to the control. force fit A class of interference fit that involves relatively large amounts of negative allowance, requires large amounts of force to assemble, and results in the inducement of relatively large stresses in the assembled parts. force-balance transmitter A transmitter design technique that utilizes feedback of the output signal to balance the primary input signal from the measuring element. The bal­ anced output signal is proportional to the measured variable. forced circulation Using a pump or fan to move fluid through a conduit or process ves­ sel. Examples include air or gases through a furnace or combustion chamber (often referred to as "forced draft"), ambient or con­ ditioned air through ductwork (often referred to as forced ventilation), or a mix­

ture of water and steam through tubes in a boiler. forced draft Air that is under the positive pressure produced by fans situated at the point where air or gases enter a unit, such as a combustion furnace or boiler. forced-draft fan A fan that supplies air under pressure to the fuel-burning equipment.

[ISA-77.41-1992] forced oscillation The oscillation of a system attribute where the period of oscillation is determined by 'an external periodic force. forced vibration Oscillation that occurs at the frequency of a driving force input. forcing 1. The act of applying control signals greater than those warranted by a gi\en deviation in the controlled variable in order to induce a more rapid rate of adjustment in the controlled variable. 2. A function of the engineering station of a Programmable Elec­ tronic System (PES), which provides the capability to override the application pro­ gram and to change the states of inputs and outputs. [ANSI/ISA-84.01-1996] Ford cup viscometer A time-to-discharge apparatus that is used primarily for deter­ mining the visc06ify of paints and varnishes. foreground 1. The information element on a background field. [ISA-5.5-1985]2. The area in memory that is designated for use by high-priority programs. The program, set of programs, or functions that gain the use of machine facilities immediately upon request. foreground/background A control system that uses two computers, one to perform the control functions and the other for data log­ ging, evaluating performance off line, per­ forming financial operations, and so on.

Either computer can perform the control functions. foreground/background processing A com­ puter system that is organized so that pri­ mary tasks dominate computer processing time when required, and secondary tasks fill the remaining time. foreground program A time-dependent pro­ gram that is initiated by request. Its urgency preempts the operation of a background pro­ gram. Contrast with background program. fore pump A vacuum pump that is operated in series with another vacuum pump. It pro­ duces vacuums at the discharge of the sec­ ond vacuum pump, which is not capable of discharging gases at atmospheric pressure. fore vacuum A space on the exhaust side of a vapor jet or pump where the ambient static pressure is below atmospheric.

214

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torglng I tour-ball tester

forging 1. Using compressive force to plasti­ cally deform and shape metal. It is usually done hot, in dies or between rolls. 2. A shaped part that is made by impact, com­ pression, or rolling. If made by rolling, the part is usually referred to as a "roll forging."

Format 1. To prepare a diskette so it can accept computer data. 2. A specific arrange­ ment of computer data. 3. To arrange a tape record, buffer, or the like so it is compatible with processing or storage standards. 4. The arrangement of the programming elements that comprise any field, record, file, or vol­ ume. 5. The basi}= parameters of a telemetry / data-acquisition sample plan. For example, the format would include the number of words per frame and frames per subframe in a sample plan. formatted ASCII A mode io which data are transferred. A file that contains formatted ASCII data is generally transferred as strings of seven-bit ASCII characters (bit eight is zero) and terminated by a line feed, form­ feed, or vertical tab. Special characters, such as null, Rubout, and tab may be interpreted specially. formatted binary A mode in which data are transferred. Formatted binary is used to transfer check-summed binary data (eight-bit characters) in blocks. Formatting , characters are start-of-block indicators, byte count, and check-sum values. formatter A hardware or software process for arranging data on tape or disk or in a buffer. form factor The physical specifications of a device, such as rack mounts, and so on. Form factor evolved from the relay terminology for contact configurations. form feed (FF) A control character that is nor­ mally used to command a printer to feed the paper to the top of the next page. form grinding The process of producing a contoured surface on a part by grinding it with an abrasive wheel whose face has been shaped to the obverse of the desired contour. forming Applying pressure to shape a mate­ rial by plastic deformation without inten­ tionally altering its thickness. formula 1. A set of parameters that distin­ guish the products that are defined by proce­ dures. The formula may include types and quantities of ingredients, along with infor­ mation such as the magnitude of process variables. It may effect procedures. 2. A cate­ gory of recipe information that includes pro­ cess inputs, process parameters, and process outputs. [ANSI/ISA-88.01-1995] formula translation system See FORTRAN.

FORTH A computer language that should have been called FOURTH (fourth-genera­ tion), but astronomer / developer Charles Moore's computer accepted only five-charac­ ter names. This object-oriented language was created to control telescopes, but its extend­ ability is the key to its ever-growing popular­ ity. Using "reverse Polish" notation, it contains applications that are useful in pro­ cess control.

F.ORTRAN. 1. "For~ulaTran;;lation." A pro­ cedure-oriented 13riguag~ for solving arith­ metic inli, logical programs and the first high­ level computer language. It is.a procedure­

oriented language that has good array-han­

dling features. Developed by IBM in 1954,

FORTRAN was known as a scientific lan­

guage because of its facility at "number

crunching" and solving engineering, mathe­

matical, and other scientific problems. 2. The

computing language that is defined as full

FORTRAN ISO R1539~1972, which is the same

as American National Standard FORTRAN

ANSI X3.9-1966.

FORTRAN compiler A processor program for FORTRAN. forward channel A data transmission chan­ nel in which the direction of transmission coincides with that in which the information is being transferred. forward compatible Designs that ensure compatibility with future versions. forward controlling elements See elements,

forward controlling. forwarding The act of accepting and retrans­ mitting network traffic. fossil fuel Coal or petroleum hydrocarbon fuel, as distinguished from nuclear fuel. fouling 1. The growth of adherent plant or animal life on submerged structures. It often leads to biological corrosion or the degrada­ tion of performance, such as the reduction of heat transfer or the increase of fluid friction.

2. The accumulation of refuse in gas passages

or on heat-absorbing surfaces, which results

in undesirable restrictions to the flow of gas

or heat.

foundry A commercial enterprise, plant, or portion of a factory where metal or glass is melted and cast. .~. four-ball tester An apparatus for determin­ ing lubrication efficiency by driving one ball against three stationary balls that are clamped together in a cup filled with the test lubricant. The effectiveness of lubrication is expressed relatively in terms of wear-scar diameters on the stationary balls.

215

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Fourier optics 1. Optical components that are used to make Fourier transforms and other types of optical processing operations. 2. A prism or grating monochromator that essentially performs a Fourier transform on the light shining on the entrance slit.

Fourier series and transform Mathematical tools for analyzing functions by decomposing them into sinusoids. four wire A normal requirement for a fullduplex circuit. Two wires are used for the transmission, and two are used for the reception. four-wire transmitter An electronic transmi tter that h~s separate wires for signal and power. fourth-generation language (4G L), fourthgeneration environment (4GE) A computer language that ipstructs the computer at a higher-level language abstraction than traditional high-level programming languages.

Any computer language that does not require traditional input process/output logic will fall into this category.

FOV Field of view (of sensors, especially optical).

FPM Feet per minute (flow velocity). Also, Fast Packet Multiplexing, a technology that integrates synchronous and asynchronous data with voice and fax signals over a composite channel, eliminating the delays associated with standard packet multiplexing by giving priority to voice and fax signals over data signals.

FPS Feet per second, in flow velocity; frames per second in video and computer imaging.

FPU Floating point unit; performs numeric calculations for the processor, specialized just for numeric calculations. Can boost screen redraws, image filtering effects, spreadsheet calculations, and similar operations by as much as 900 percent.

FQ Flow quantity when used in the first two alpha character positions of ISA-instrument function tag. [ANSI/ISA S5.1-1984 (R1992)] fraction 1. In the classification of powdered or granular solids, the proportion of the sample (by weight) that lies between two stated particle sizes. 2. In chemical distillation, the proportion of a solution of two liquids that consists of a specific chemical substance. fractional distillation A thermal process in which a mixture of liquids that boil at different temperatures is heated at a series of increasing temperatures, and the distillates that are boiled off at each temperature are collected separately.

fractional factorial designs A subclass of factorial designs that reduces the number of experiments to be performed by exploring systematically only a fraction (such as one half) of the input variable space. fractionating column An apparatus for fractional distillation in which rising vapor and falling liquid are brought into intimate contact. fraction defective In quality control, the average number of. units of product that Contain one or more defects for each 100 units of product in a given lot. fractography The study of fracture surfaces, especially for the purpose of determining the causes of failure and relating these causes to the macrostructural and microstructural characteristics of parts and materials. fracture test A method for determining composition, grain size, case depth, or material soundness by breaking a test specimen and examining ll1e fracture surface for certain characteristic fea tures. fragmentation [Comp]1. In computing, the tendency of files in disk storage to be divided up into many small areas scattered around the disk. [Comm]2. In communications, the process of breaking network transmission units into smaller units.

FRAM Ferroelectric random access memory is high density with the high speeds of DRAM and SRAM and the nonvolatility of ROM; also called "Flash RAM;" see flash memory.

frame 1. A group of digits that is transmitted as a single unit and over which a coding procedure is usually applied for the purposes of synchronization or for error control. Also called block. 2. A set of consecutive digit time slots in which the position of each digit time slot can be identified by referring to a framing signal. Note: This definition is taken from IEEE Standard 100-1984. [ANSI/ISA-50.02, Part 2-1992]3. The image in a computer display terminal. 4. In time-division multiplexing, one complete commutator revolution, which includes a single synchronizing signal or code. frame code complement (FCC) The subframe synchronization method in 'v',(hich the frame synchronization code is complemented so as to signal the beginning of each subframe. frame rate (FRATE) The ra te, or the pulses that clock that rate, of rotation of a data multiplexer "wheel." frame synchronization pattern A unique code, coded pulse, or interval used to mark the start of a commutation frame period.

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frame synchronizer I frequency, gain crossover frame synchronizer (FSY) Telemetry hardware that recognizes the unique signal that indicates the beginning of a frame of data. A typical frame synchronizer "searches" for the code, "checks" for the recurrence of the code in the same position for several frame periods, and then "locks" on the code. framework The load-carrying members of an assembled structure. framing error An error that results from transmitting or receiving data at the wrong speed. A character of data will appear to have an incorrect number of bits. free ash Ash that is not included in the fixed ash. free-electron laser A laser in which stimulated emission is produced by a beam of free electrons passing through a magnetic field that periodically (in space t-ather than time) alters its polarity. free field Ideally, a wave field or potential energy field in a homogeneous, unbounded medium. However, practically speaking, a free field is a field where boundary effects are negligible over the useful portion of the medium. free-field frequency response For a piezoelectric sound-pressure transducer, the ratio, as a function of frequency, of the transducer's .' output in a sound field to the free-field sound pressure that exists at the transducer location in the absence of the transducer.

[ISA-37.10-1982 (R1995)] .. fre~-field grazing incidence response A free-field frequency response of a piezoelectric sound-pressure transducer in which the sound incident is parallel to a specified sensing surface of the microphone. free field (sound) A free sound field is one' tha t exists in a homogeneous, isotropic medium that is free of any acoustically reflecting boundaries. [ISA-37.10-1982 (1995)] freefit A type of clearance fit that has a relatively large allowance. It is used when the accuracy of assembly is not essential, when large temperature variations may occur, or both. Also known as "free-running fit." free flow A condition in which the liquid surface downstream of the weir plate is far enough below the crest so that air has free access beneath the nappe. See Happe. free gyroscope A gyro wheel that is mounted in two or more gimbal rings so that its spin axis can maintain a fixed position in space. free impedance A transducer characteristic that is equal to the input impedance when the load impedance is zero.

free-machining A material description that indicates some alteration of chemical composition in order to substantially improve machinability. Such alteration could be the addition of sulfur, phosphorus, or lead to steel or lead to nonferrous metals. Also called"free-ell tting." free oscillation The periodic variation of some system variable when the externally appriedforceseithE;r do.I)o "York or are derived from an in¡variant potential. free running A term-used to describe the data acquisition of an analyzer. In this process, the instrument acquires the next time block when it is finished processing the previous time block and is ready for more data.

It continuously operates this way, updating the display. free-standing A control center or enclosure that will be stable in its normal position without exter~al br,:cing or bolting to other structures. ; â&#x20AC;˘.:.....- . free vibration Oscillation that occurs at a natural frequency, after an initial force input. free water The amount of water that is released when a wet solid is dried to its equilibrium moisture content. freeze To hold the contents of a register (time, for example) until they have been transferred to another device. freeze-up 1. The abnormal operation of a refrigeration unit because ice has formed on the heat-absorbing elements. 2. The stoppage of rotational motion becau~e of radial expansion or adhesive welding between a bearing and its journal. Also called "seizure." freezing point The temperature at which equilibrium is attained between liquid and solid phases of a pure sub~;tance. The term is also applied to compounds and alloys that undergo isothermal liquid-solid phase transformation.

French coupling A coupling that has a righthand and a left-hand thread. frequencies The harmonics of a periodic variable. frequency 1. The number of cycles over a specified time through which an event occurs. The reciprocal is called the ':period."

2. The number of cycles a periodic variable passes through per unit time. 3. The rate of signal oscillation in hertz. frequency, damped The apparent frequency of a damped oscillatory time response of a system as a result of a nonoscillatory stimulus. [ANSl/ISA- 51.1-1979 (R1993)] frequency, gain crossover 1. On a Bode diagram of the transfer function of an element

217

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frequency, natural/frequency modulation

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or system, the frequency at which the gain becomes unity (and its decibel value zero). 2.

Of integral control action, the frequency at which the gain becomes unity. [ANSI/ISA51.1-1979 (R1993)] frequency, natural 1. The frequency at which a part, or system, will oscillate if excited with an impulse. 2. The frequency of free (not forced) oscillations of the sensing element of a fully assembled transducer. Note 1: Natural frequency is also defined as the frequency of a sinusoidally applied measurand at which the transducer output lags the measurand by 9au. Note 2: Natural frequency is applicable at room temperature unless otherwise specified. Note 3: Also see frequency, resonant and frequency, ringing. These are considered of more practical value than natural frequency.

[ISA-37.1-1975 (R1982)] \ frequency, phase crossover Of a loop transfer function, the frequency at which the phase angle reaches Âą180 . [ANSI/ISA-51.11979 (R1993)] frequency, resonant The measurand frequency at which a transducer responds with maximum output amplitude. Note 1: When major amplitude peaks occur at more than one frequency, the lowest of these frequencies is the resonant frequency. Note 2: A peak is considered major when it has an amplitude that is at least 1.3 times the amplitude of the frequency to which the specified frequency response is referred. Note 3: For subsidiary resonance peaks, see resonances. [ISA37.1-1975 (R1982)] frequency, ringing The frequency of the oscillatory transient that occurs in the transducer output as a result of a step change in measurand. [ISA-37.1-1975 (R1982)] frequency, undamped (frequency, natural) 1.

Of a second-order linear system without damping, the frequency of free oscillation in radians or cycles per unit of time. 2. The value W II of any system whose transfer function contains the quadratic factor 52 + 2zw ns + w 1I 2, where s=complex variable, z=constant, and wlI=natural frequency in radians per second. 3. Of a closed-loop control system or controlled system, a frequency at which continuous oscillation (hunting) can occur without periodic stimuli. Note: In linear systems, the undamped frequency is the phase crossover frequency. With proportional control action only, the undamped frequency of a linear system may be obtained in most cases by raising the proportional gain until continuous oscillation occurs. [ANSI/ISA51.1-1979 (R1993)]

frequency band The continuum between two specified limiting frequencies. frequency departure The amount by which a carrier frequency or center frequency varies from its assigned value. frequency deviation The peak difference between the instantaneous frequency of a modulated wave and the frequency of the unmodulated carrier wave. frequency distortion A form of distortion in which the rel~tive l}lagnitudes of the components of a cOrrlple'x wave are changed during transmission. . frequency divider An electronic circuit or device whose output-signal frequency is a proper fraction of its input-signal frequency. frequency-division multiplex (FDM) A system for transinitting information about two or more quantities (measurands) over a common channel by dividing the available frequency bands. Amplitude, frequency, or phase modulation of the subcarriers may be employed. frequency division multiplexer (FDM) A device that divides the available transmission frequency range into narrower banks, each of which is used for a separate channel. frequency-divisional multiplexing The combining of two or more Signals at different frequencies so they can be transmitted as one signal. This can be done electronically or it can be done optically by using two or more light sources of different wavelengths. frequency domain 1. Pertaining to a method of analvsis, in which one does not deal with functio'ns of time explicitly, but with their Laplace or Fourier transforms, which are functions of frequency. It is particularly useful for fixed linear systems. 2. Vibration, represented as a graph of amplitude versus frequency. frequency meter An instrument for determining the frequency of a cyclic signal, such as an alternating current or radio wave. frequency-modulated output An output that takes the form of frequency deviations from a center frequency, where the deviation is a function of the applied measurand. [ISA37.1-1975 (R1982)] '. frequency modulation' (FM) 1. The process (or the result of the process) in which the frequency deviates from the unmodulated carrier in proportion to the instantaneous value of the modulating signal. 2. A type of electronic circuit that produces an output signal whose frequency has been modified by one or more input signals. See also modulated wave. 3. In telemetry, the modulation of the

218

frequency monitor I frequency shift keying frequency of an oscillator so as to indicate data magnitude. The sine wave of a carrier has its frequency modified in accord with the information that is being transmitted.

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, frequency monitor An instrument that deter, mines the amount that a frequency deviates from its assigned value. frequency multiplication The process of . generating harmonics of the frequency of a lightwave through nonlinear interactions of the lightwave with certain materials. Frequency doubling is equivalent to dividing the wavelength in half. High-power beams are needed in order for the nonlinear interaction to occu r. , frequency multiplier An electronic circuit or : device whose output-signal frequency is an I exact multiple of its input-signal frequency. . frequency output Output that takes the form of a frequency that varies as a function of applied measurand (e.g., angular speed and flow rate). [ISA-37.1-1975 (R1982)] frequency phase control regulation A regulation technique in power supplies that can control the phase of either the primary or secondary. element. It usually employs silicon-controlled rectifiers (SCRs). frequency response 1. The behavior of device output as a function of input, both with respect to time. 2. The change with frequency of the sensitivity with respect to the reference sensiti'.'ity, for a sinusoidally vary-

219

ing acceleration applied to a transducer within a stated range of frequencies, usually specified as "within ±_ _ percent of the reference sensitivity from__ to __ cps." The applicable total capacitance and load resistance should be stated. 3. The change with frequen~y of the output/measurand amplitude raho (and of the phase difference between output and measurand) for a sinusoidall)' varying·mea~urand that is applied to a transducer within'a stated range of measur~nd frequencies. Note: 1: Frequency response IS usually specified as"within ± [number] percent (or ± [number] dB) from [number] to [number] hertz." Note 2: Frequency response should be referred to a frequency that is within the specified measurand frequency range as well as to a specific measurand value. [ISA-37.1-1973 (R1982)] 4. A measure of the effectiveness with which a circuit or device transmits signals of different frequenc~es. It is usually expressed as a graph of magrutude or phase of an output signal as a function of frequency. Also known as "amplitude-frequency response" and "sine-wave response." 5. For a linear system in sinusoidal steady state, the ratio of the Fourier transform of the output signal to the Fourier transform of the corresponding input signal. 6. The response of a component, instrument, or control system to input Signals at varying frequencies. frequency response, calculated The frequency response of a transducer as calculated from its transient response, its mechanical properties, or its geometry, and so identified, [ISA-37.1-1975 (R1982)] frequency-response analyzer An instrument that measures the gain or loss of signal level through an electronic circuit as a function of frequency. frequency-response characteristic In process instrumentation, the frequency-dependent relation, in both gain and phase, between steady-state sinusoidal inputs and the resulting fundamental steady-state sinusoidal outputs. Note: Frequency response is commonly plotted on a Bode diagram."

[ANSI/ISA-51.1-1979 (R1993)]:.... frequency-response method A method of tuning a process control 100? for optimum operation by properly selecting the controller settings. This method is based on a study of the frequency response of the open process control loop. frequency shift keying (FSK) Modulation that is accomplished by switching from one

II

frequency stability / frost plug discrete frequency to another discrete frequency. frequency stability 1. A measurement of how well the output frequency (or, equivalently, the emitted wavelength) of a laser stays constant. In some types, the emitted wavelength tends to drift because of such factors as the changing temperature of the laser itself. 2. A statement of the deviation with time, temperature, or s.upply voltages of an electronic oscillator when compared to a standard. frequency swing A characteristic of a fre~ quency~modulation system that is equal to the difference between the maximum and minimum design values of instaptaneous frequency in the modulated wa\(e.路. frequency telemetering A system for transmitting measurements in which the information values are represented by frequencies within a specific band. The specific frequency is determined by the percentage of full scale equivalent to the current value of the measured variable.

Fresnellens A lens whose surface is composed of a number of concentric lens sections that have the same focal length as is desired for the larger lens. Typically, for high-quality optical applications, the smaller lenses are concentric circles. This technique is used to compress a short focal-length optical component into a thickness that is much less than that of a plane-convex lens of the same material and focal length.

Fresnel reflection A reflection that occurs at the planar junction of two materials that have different refractive indices. This is not a function of angle of incidence. fretting A form of wear that occurs between closely fitting surfaces that are subjected to cyclic relative motion of very small amplitude. It is usually accompanied by corrosion, especially of the very fine wear debris. Also known as "chafing fatigue," "fretting corrosion," "friction oxidation," "molecular attrition," "wear oxidation," and, in rolling-element bearings, "false Brinelling." friable Capable of being easily crumbled, pulverized, or otherwise reduced to powder. friction See friction error. frictional error See error,frictional. friction error The maximum change in output, at any measurand value within the specified range, before and after friction within the transducer has been minimized by dithering. [ISA-37.1-1975 (R1982)] friction-feed printer A printer that uses the pressure of a platen to advance the paper.

friction-free error band The error band that is applicable at room conditions and with the frictions within the transducer minimized by dithering. [ISA-37.1-1975 (R1982)J friction oxidation See fretting. friction tape A type of cotton tape that is impregnated with a sticky, moisture-resistant compound and used to cover and insulate exposed electrical connections or terminations. It has been largely replaced by electrical tape m.a~e.of polyvinyl chloride resin backed witli. q sticky adhesive.. friction-tube viscometer A device for measuring viscosity by determining the pressure drop across a friction tube as the fluid is pumped through it. frigorimeter A thermometer for measuring low temperatures. frit Fusible ceramic mixture that are used to make ceramic glazes and porcelain enamels from unspecified apparatuses. [ISA-12.02.011999 (lEe 60079-11 Mod)] frit seal A hermetical seal for enclosing integrated circuits and other electronic components. It is made by fusing a mixture of metallic powder and glass binder. from-to tester A type of electronic test equipment for checking the continuity between two points in a circuit. front end An enigmatic term used by some to mean the operator interface or the application-specific aspects of a computer program.

Others define it to mean that part of the control system that is directly connected to the process sensors and instruments connected to the process. front-end processor 1. A dedicated processor for performing communication functions so as to offload other processors within the same device. It is that portion of the system that first receives the rrocess or plant data, usually for signal conditioning and/ or multiplexing. 2. A device that receives computer data from other input devices, organizes such data as specified, and then transmits this data to another computer for processing. 3. The computer equipment that is used to receive plant signals, including analog-to-digital converters and the associated cop-trois. frost plug A device for detennining liquid level when the contents of a tank are at a temperature below O掳c. It consists of a side tube that resembles a sight glass but has a series of closed tubes (plugs) at different levels instead of the glass. The tubes below liquid level are cooled so that moisture from the atmosphere forms frost on them, while the tubes above liquid level remain frost free.

220

trothing I tull-scale value

[

frothing Production of a layer of relatively stable bubbles at an air-liquid interface.

Frothing can be accomplished by any of several methods, including aeration, agitation, or chemical reaction. In many instances, it is an undesired side effect of an operation, but sometimes it is an essential element of the operation, as in froth flotation for separating a mineral from its are.

FRP Fiber-reinforced plastic; sometimes used for instrurnent enclosures.

FSK Frequency-shift keying; method of data transmission using frequencies to indicate the state of the b~t being transmitted, see AM and PM. FTAM File Transfer Access and Management; ISO protocol and part of MAP layer 7.

FTP File transfer protocol; upper-level TCP / IP service that allows files tq be copied or moved across a network. fuel 1. A substance that contains combustible material that is used for generating heat.

Coal, oil, and gas are fuels as referenced in the relevant ISA standard. [ISA-77.41-1992]2.

Any material that will burn or otherwise react so as to release heat energy. Common fuels include coal, charcoal, wood, and petroleum products (fossil fuels), which burn, and ; uranium, which undergoes nuclear fission. fuel-air mixture A mixture of fuel and air. fuel-air ratio The ratio of the weight, or vol. ume, of fuel to air. fuel gas A combustible gaseous substance . that is used as a fuel. .fuel oil Any oily hydrocarbon liquid that has a flash point of at least lOOcF (38'C), which can be burned to generate heat. fuel trip The automatic shutoff of a specific fuel as the result of an interlock or operator action. [ANSI/ISA-77.44.01-2000] fulchronograph An instrument for recording lightning strikes electromagnetically. fulgurator An atomizer that is used in flame analysis to spray into the flame the salt solution to be analyzed. full adder A computer logic device that accepts two addends and a carry input and produces a sum and a carry output. full annealing An imprecise term that implies heating to a suitable temperature, followed by controlled cooling for the purpose of producing a condition of minimum strength and hardness. full ball A closure member that has a complete spherical surface with a flow passage through it. [ANSI/ISA-75.05.01-2000] full bridge In strain gauges, such as in force or pressure sensors, the condition in which

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all four legs of a Wheatstone bridge configuration are active in the development of a signal. full duplex 1. Communications that appear to have information transfer in both directions (transmit and receive) at the same time.

2. The electronic transmission of data simultaneously in two directions. See dllplex,fllll. full-duplex transmission The simultaneous, two-way communication between devices. full-hard te.mper. A lev~l o£hardness and strength fat nonf€rrous alloys and some ferrous alloys. It corresponds to a cold ":yorked state beyond which the material can no longer be formed by bending. full range (F.R.) The algebraic difference between the minimum and maximum values for which a device is specified. [ISA-RP55.11975 (R1983)] Fuller's earth A highly absorbent, claylike material formerly used to remove grease from woolen cloth, but now used principally as a filter medium. full-face gasket A flat gasket that contacts the entire flat contact surface of two mating flanges, extending past the bolt holes. This term applies to flat face flanges only. [ANSI! ISA-75.05.01-2000] full-motion imaging A video image that is completely smooth, without stutter. See ras-

ter imaging. full-scale (ES.) The maximum absolute value for which a device is specified. [ISA-RP55.11975 (R1983)] See range. full-scale error The difference between the actual and ideal output from an analog-todigital converter (ADC) or digital-to-analog converter (DAC) for full-scale input.

Expressed in millivolts, percentage of full range or least-significant bits (LSBs). Also called "gain error." full-scale gas concentration One hundred percent of the actual marked full-scale concentration value. [ANSI!ISA-12.13.01-2000] full-scale output 1. The algebraic difference between the end points. Note: Sometimes expressed as "± [half the algebraic difference]," for example, "±2.5 volts." [ISA-37.11975 (R1982)] 2. The algebraic difference between minimum output and max.ifnum output. .. full-scale value 1. The largest value of a measured quantity that can be indicated on an instrument scale. 2. For an instrument whose zero is between the ends of the scale, the sum of the absolute values of the measured quantity corresponding to the two ends in the scale.

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tull-wave rectifier I function switch

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full-wave rectifier An electronic circuit that converts an AC input signal into a DC output signal. Current flows in the output circuit during both halves of each cycle in the input signal. function 1. The purpose of a device, or an action performed by it. [ANSI/ISA-5.1-1984 (R1992)]2. A specific purpose of an entity. 3.

One of a group of actions that is performed by an entity in accomplishing its purposes.

[ISA-TR50.02, Part 9-2000] 4. In communications, a mach~ne action such as a carriage return OTline feed. 5. A closed subroutine that returps a value to the calling routine when it concludes. 6. The operation called for in a computer software instruction. functional design The specification of the working relations between the parts of a system in terms of their characteristic actions. functional earth tenninal A terminal by which electrical connection is made directly to a point of measuring, a control circuit, or a screening part. It is intended to be earthed for any functional purpose other than safety.

Note: For measuring equipment, this terminal is often termed a "measuring earth terminal." [ANSI!ISA-82.02.01-1999 (IEC 1010-1 Mod)] functional diagram A diagram that represents the functional relationships among the parts of a system. functional fidelity The degree of similarity between the simulator and the reference plant relative to the static and dynamic response of the equipment and controls.

[ANSI lISA -77.20-1993] functional program A routine or group of routines that, when considered as a whole, completes some task with minimal interaction with other functional programs other than to obtain data and signal its completion of its task. For example, a group of routines that take data from an analog scanner and store it on a bulk storage device might be considered a functional program. functional requirement A requirement that specifies some function that a particular system or system component must be capable of performing. It is usually formally written, especially in process validation. functional specification A document that tells exactly what the system should do, what will be supplied to the system, and what is expected to come out of it. functional test A test that is performed on a subsystem or loop to verify whether an instrument or piece of equipment has responded properly to simulated inputs and

outputs. Individual "loop" drawings, electrical ladders, and wiring diagrams are usually the basis for this test. functional testing [Safe] 1. In a safety context, a periodic activity to verify that the safety instrumented system is operating in conformity with the safety requirement specifica tions testing. [ANSI! ISA-84.01-1996J [Comp] 2. In computing, inputting normal and abnormal test cases and then evaluating the outputs against those expected. Functional testing etui. apply to computer software or to a total system. Also known as "black box testing" because source code is not needed. functional unit An entity 9f hardware or software, or both, that is capable of accomplishing a specified purpose. [ISA-TR50.02, Part 9-2000] function block A named block that consists of one or more input and output parameters.

[ISA-TR50.02, Part 9-2000] function block diagram 1. A diagram that indicates the functions of the principal parts of a total system and also shows the important relationships and interactions among these parts. 2. A graphical language of programmable controllers that allows program elements (such as PID and other algorithms) to appear as blocks that are "wired" together as shown in a visual presentation similar to a circuit diagram. One of five languages accepted under the IEC 1131 standard for PLCs. See instruction list, ladder logic, structured text, and sequential fUl1ction chart. function block type A software element that specifies the qualities that are common to all instances of the type. [ISA-TR50.02, Part 92000J function generator A multi-waveform signal source that typically offers a complete set of functions, including sine waves, square v"aves, sawtooth waves, ramps, and sometimes arbitrary waveforms. function keys Special keys on a computer keyboard that instruct the computer to perform a specific operation. function subprogram An independently written program (and treated as such by the compiler), which may consistfuf any number of statements that are executed when it is called. See also subroutine and SUbprogram. function switch A circuit that has a fixed number of inputs and outputs. It is designed such that the output information is a function of the input information, and each is expressed in a certain code, signal configuration, or pattern.

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function table / fusion zone

1 1.

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function table 1. The two or more sets of information that are arranged such that an entry in one set selects one or more entries in the remaining sets. 2. A dictionary. 3. A device that is constructed of hardware or a subroutine that can either decode multiple inputs into a single output or encode a single output into multiple outputs. 4. A tabulation of the values of a function for a set of values of the variable. fundamental frequency The frequency of a ': sinusoidal function that has the same period as a complex periodic quantity. fundamental mode 1. The mode of a waveguide that has the lowest critical frequency. 2. A type of sequential circuit in which there is only one input change at a time and no further change occurs until all states are stabilized. fundamental natural frequency The lowest frequency in a set of natural frequencies. furnace 1. An apparatus in which heat is liberated and transferred directly or indirectly to a solid or fluid mass. It generally operates at a higher temperature than an oven. 2. An enclosed space provided for the combustion of fuel. [ISA-77.41-1992]3. An apparatus for liberating heat and using it to produce a physical or chemical change in a solid or liquid mass. Most often, the heat is produced by burning a fossil fuel, passing electric current through a heavy-duty resistance element, generating and sustaining an electric arc, or electromagnetically inducing large eddy currents in the charge.

FURNACE PRESSURE (DRAFT) TRANSMITTERS (SENSOR A B C LOCATIONS)

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Typical Furnace Pressure Control Functional Diagram furnace draft The draft in a furnace as measured at a point immediately in front of the highest point at which the combustion cases leave the furnace.

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furnace pressure The pressure of gases in the furnace. See also draft. furnace volume The cubical contents of the furnace or combustion chamber. fuse 1. Any of several devices for detonating an explosive by, for example, elapsed time, command, impact, proximity, or thermal effects. 2. A link in a series, which has a source of power that will open a circuit if a fault of predetermined magnitude occurs in the路pow~red device. 11le link is a piece of fusible metal that will melfwhen excess current flows. fused fiber optics A number 6f separate fibers that are melted together to form a rigid, fused bundle for the purpose of transmitting light:Fused fiber optks maybellsed. for transmitting images or simply tor illumination; they are not necessarily coherent bundles of fibers. fused silica The term that is usually applied to synthetic fused silica, which are formed by chemically combining silicon and oxygen so as to produce a high-purity silica. Optical glass is made by melting high-purity sands, while fused quartz is made by crushing-and melting natural quartz. See silica glass. fuse-protected shunt diode barrier A network that is designed to limit current and voltage. It consists of a series fuse, voltagelimiting shunt diodes, and a current-limiting resistor or other current-limiting components. The fuse is intended to protect the diodes from open circuiting when high-fault currents flow. [ANSI/ISA-RP12.6-1995] fuse pullout A removable fuse holder that can be removed when fuses must be replaces or an electrical circuit needs to be opened. fuse rating, In The current rating of a fuse.

[ANSI/ISA-12.25.01-1998 (lEe 79-05 Mod)] fusible alloy An alloy that has a very low meltin~ point, in some instances approaching 150 F (65掳C). The alloy is usually based on Bi, Cd, Sn, or Pb. Fusible alloys have varied uses, the most widely known being solders and fusible links for automatic sprinklers, fire alarms, and other safety devices. fusible plug A hollowed, threaded plug in which the hollowed portion is fill~ with a material with a low melting point. It is usually placed at the lowest permissible water level. fusion welding Any welding process that involves melting a portion of the base metal. fusion zone In a weldment, the area of base metal that was melted, as determined by examining a cross section through the weld.

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future alarm point / fuzzy set

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future alarm point See alarm point. futurebus+ A fast standard for scalable, backplane interconnect that was adapted by IEEE in September 1991. It has a 32- or 64-bit rate, up to 175 MBps, and no license fees. fuzzifier A function that assigns a variable to one or more fuzzy sets. fuzzy logic A reasoning approach and computing method that is used to modellinguistic expressions (such as "somewhat more than") that have nonbinary truth values. It has been used with rID algorithms in process control, especially for nonlinear processes.. fuzzy set A set in which the characteristic function that determines the membership of an object in the set is not limited to the two values 1 (for membership in the set) and 0 (for nonmembership)~ Instead, the characteristic function can also take on a partial value between a and 1. This function is called a . "fuzzy value."

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